Bi- and tetranuclear polyfluorophenyl-bridged gold(I) complexes

The reaction of RAuL (R = 2,4,6-C₆F₃H₂, 3,6-C₆F₂H₃, 4-C₆FH₄ or 3-CF₃C₆H₄; L = PPh₃ or AsPh₃) or RAudpeAuR with inorganic acids HA (A = ClO₄, BF₄ or PF₆) leads to binuclear complexes of the types [R(AuL)₂]A or [R(Au₂dpe)]BF₄. Similarly, reaction of NBu₄[Au(2,4,6-C₆F₃H₂)₂] with HPF₆ yields the tetranuclear complex Au₄(2,4,6-C₆F₃H₂)₄. Addition of RAuL to solutions obtained by treating ClAuL with AgA also gives compounds of the type [R(AuL)₂]A.     

Demercuriation reactions of the complexes [(PPh3)2RPtHgR′] containing platinum-mercury bonds

The compounds [(PPh₃)₂,RPtHgR′] (R = CH₃, R′= 2,5-C₆H₃Cl₂, 2,3,4- and 2,4,6-C₆H₂Cl₃, 2,3,4,5-, 2,3,4,6- and 2,3,5,6-C₆HCl₄, C₆Cl₅; R = Et, R′ = 2,5-C₆H₃Cl₂, 2,4,6-C₆H₂Cl₃; R = 2-C₆H₄Cl, R′=2-C₆H₄(CH₃)) have been prepared by the reactions of RHgR′ with Pt(PPh₃)₃, in order to study their possible use as intermediates in the preparation of diorganoplatinum complexes with different organic ligands. The dependence of J(³¹P-¹⁹⁵Pt) on slight differences in the electronic character of the ligand R′ in the series of compounds [(PPh₃)₂(CH₃)Pt-HgR′] has been studied.     

Polyfluorophenylgold(I) complexes

Neutral polyfluorophenyl complexes of the type RAuL and RAuL-LAuR and anionic complexes of the type [AuR₂]^? (R = 2,3,5,6-C₆F₄H, 2,4,6-C,F₃H₂, 3,6-C₆F₂H₃, 4-C₆ FH₄ or 3-CF₃C,H₄) are obtained by the reaction of ClAuL (L = PPh₃, P(cyclohexyl)₃, AsPh₃ or tetrahydrothiophen; L-L = Ph₂PCH₂PPh₂ or Ph₂PCH₂CH₂PPPh₂) with an organolithium derivative and/or the replacement of the initial ligands L by other mono- or bi-dentate ligands.The outcome of the reaction of [AuR₂]^? with [Au(PCy₃)₂]⁺ (Cy = cyclohexyl), depends on the nature of the ligand R; thus with R = 3,6-C₆,F₂H₃ the product is [Au(PCy₃)₂][AuR₂], while with R = 2,4,6-C₆F₃H₂, the product is [Au(PCy₃)(2,4,6-C₆F₃H₂)].     

Solvent,ligand and temperature effects on the rates of reactions of cis-[PdCl2(CNR)(L)] with secondary amines

The kinetics of the reaction of cis-[PdCl₂(CN-p-C₆H₄Cl)(PPh₃)] with N-methylaniline yielding the carbene derivative cis-[PdCl₂ {C(NH-p-C₆H₄Cl)NMePh} (PPh₃)] have been studied in various solvents such as acetone, 1, 4-dioxane, 1,2-dichloroethane, and benzene. Overall rates for the stepwise process increase with decreasing ability of the solvent to form hydrogen bonds with the attacking amine. A kinetic study is also reported for the reactions of N-methylaniline with cis- [PdCl₂(CN-p-C₆H₄Me)(L)] in 1,2-dichloroethane (L = P(OMe)₃, P(OMe)₂Ph, PPh₃. PMePh₂, PMe₂Ph, PEt₃, PCy₃). The cis ligand L affects reaction rates through both steric and electronic factors. The nucleophilic attack of the amine on the CN carbon atom of coordinated isocyanide is favoured by low steric requirements and high π-acceptor ability of L. The activation parameters for the bimolecular nucleophilic attack when L = PPh₃ are △H^≠₂ = 9.8 ± 0.7 kcal/mol and △S^≠₂ = — 30 ± 2 e.u.     

Crown compounds for anions. Unusual complex of trimetric perfluoro-o-phenylenemercury with the bromide anion having a polydecker sandwich structure

Here we show that cyclic trimetric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ is capable of forming complexes with [PPh₄]⁺Br⁻, [PPh₃Me]⁺I⁻ and [PPh₄]⁺Cl⁻ of the composition [(o-C₆F₄Hg)₃X]⁻ [PR₃R′]⁺ (X = Br, R = R′ = Ph; X = I, R = Ph, R′ = Me) or {[(o-C₆F₄Hg)₃X₂}²⁻[PR₃R′]⁺₂ (X = Cl, R = R′ = Ph). An X-ray study of the complex with [PPh₄]⁺Br⁻ revealed that it has the unusual structure of the polydecker bent sandwich wherein each Br⁻ anion is coordinated with six mercury atoms of two neighbouring molecules of (o-C₆F₄Hg)₃.     

Synthesis and redistribution reactions of asymmetric σ-arylplatinum(II) complexes containing 4,7-phenanthroline

The mononuclear σ-aryl complexes of the type trans-[Pt(σ-C₆H₄R)(4,7-phen)(PPh₃)₂]OTf (R=4-CO₂Si^tBuPh₂, 4-CONHMe, 3-CO₂Si^tBuPh₂, 3-CONHMe; OTf=trifluoromethanesulfonate) containing a monodentate 4,7-phenanthroline (4,7-phen) ligand were prepared by an oxidative addition reaction of an aryl iodide with Pt(PPh₃)₄ to yield the key iodoplatinum(II) precursors trans-[PtI(σ-C₆H₄R)(PPh₃)₂], followed by halogen metathesis with one equivalent of 4,7-phen. The reaction of trans-[Pt(σ-C₆H₄R)(4,7-phen)(PPh₃)₂]OTf with labile complexes of the type trans-[Pt(OTf)L₂(σ-C₆H₄R′)] (L=PEt₃, R′=H; L=PPh₃, R′=4-CO₂Si^tBuPh₂, 3-CO₂Si^tBuPh₂, 3-CONHMe) afforded the asymmetric dinuclear complexes of the type trans-[Pt(σ-C₆H₄R)L₂(μ-4,7-phen)Pt(σ-C₆H₄R′)L′₂](OTf) ₂ (L=PPh₃, R=4-CO₂Si^tBuPh₂, L′=PEt₃, R′=H; L=L′=PPh₃, R=4-CONHMe, R′=4-CO₂Si^tBuPh₂; R=4-CO₂Si^tBuPh₂, R′=3-CONHMe; R=3-CONHMe, R′=3-CO₂Si^tBuPh₂) in which the 4,7-phen acts as a bridging bidentate ligand. The novel dinuclear species undergo an unusual redistribution reaction that is essentially thermoneutral at 298 K. The exchange process involves facile cleavage of a Pt-N bond and the rapid exchange of trans-[PtL₂(σ-aryl)] units in the equilibrium mixture.     

Gold(III) adducts of 2-vinyl- and 2-ethylpyridine and cyclometallated derivatives of 2-vinylpyridine: Crystal structure of the cyclometallated derivative [Au(k-C,N-CH2CH(Cl)-C5H4N)(PPh3)Cl][PF6]

Reaction of Na[AuCl₄] with 2-vinylpyridine (vinpy) and 2-ethylpyridine (etpy) affords the N-bonded adducts Au(Rpy)Cl₃ (R = CH₂CH, vinpy; CH₃CH₂, etpy). Cationic adducts, [Au(vinpy)₂Cl][X]₂ (X = BF₄, PF₆) and [Au(etpy)₂Cl₂][BF₄], were also obtained by reaction of Au(Rpy)Cl₃ with Rpy (1:1) and excess NaBF₄ or KPF₆. Thermal activation of Au(vinpy)Cl₃ in water gives the five-membered cycloaurated derivative [Au(k²-C,N-CH₂CH(Cl)-C₅H₄N)Cl₂] formally resulting through a trans nucleophilic addition of a chloride onto the CC bond. No cyclometallated derivatives are obtained by reactions of Au(etpy)Cl₃. An X-ray crystal structure determination on the PPh₃ derivative [Au(k²-C,N-CH₂CH(Cl)-C₅H₄N)(PPh₃)Cl][PF₆] was carried out.     

A novel cis-push–pull effect in cycloruthenated azobenzene thiocarbonyl-containing complexes: crystal and molecular structures of [RuX(CS)(η-C,N-C6H4N=NPh)(PPh3)2](X=Cl, I)

Treatment of [RuHCl(CS)(PPh₃)₃] with Hg(o-C₆H₄N=NC₆H₅)₂ affords [RuCl(CS)(η²C,N-o-C₆H₄N=NC₆H₅)(PPh₃)₂] (1) in good yield, where the cyclometallated azobenzene ligand coordinates through an ortho-C and one azo-N to give a five-membered chelate ring. Reaction of 1 with AgNO₃ followed by NaBr or NaI affords the chloride-exchanged products [RuX(CO)(η²C,N-o-C₆H₄N=NC₆H₅)(PPh₃)₂] (2, 3), whereas reaction of 1 with AgOC(O)Me or NaS₂CNEt₂·2H₂O gives the halide mono-phosphine-substituted complexes [Ru(CS)(LL)(η²C,N-o-C₆H₄NNC₆H₅)(PPh₃)] (4, 5). In the solid-state structures of 1 and 3 there are significant changes in the bond lengths for the cyclometallated azobenzene ligand are observed relative to free azobenzene. These are discussed, with the aid of spectroscopic and crystallographic data, in terms of a cis-push–pull effect.     

Group V complexes of the tricarbonyl(η-cycloheptatrienylium)molybdenum cation and their reduction to monosubstituted derivatives of tricarbonyl(1-6-η-cycloheptatriene)molybdenum

Reaction of [(η-C₇H₇)Mo(CO)₃][PF₆] with certain Group V donor ligands afforded monosubstituted complexes [(η-C₇H₇)Mo(CO)₂L][PF₆] (L = P(OPh)₃, PPh₃, PPh₂Me, PPhMe₂, AsPh₃, SbPh₃). These were reduced by NaBH₄ to the corresponding cycloheptatriene complexes (1-6-η-C₇H₈)Mo(CO)₂L. In addition, the preparation of alkylcycloheptatriene complexes (1-6-η-C₇H₇R)Mo(CO)₂L (R = Me, L = P(OPh)₃, PPh₃, PPh₂Me; R = t-Bu, L = PPh₃) is described. Spectroscopic properties, including ¹³C NMR, are reported.     

Carbonyl rhodium(I) complexes with α-diimines ligands

The reactions of [Rh(CO)₂Cl]₂ with α-diimines, RN=CR′-CR′=NR (R = c-Hex, C₆H₅, p-C₆H₄OH, p-C₆H₄CH₃, p-C₆H₄OCH₃, R′ = H; R = c-Hex, C₆H₅, p-C₆H₄OH, p-C₆H₄OCH₃; R′ = Me) in 2:1 Rh/R-dim ratio gave rise to ionic compounds [(CO)₂Rh.R-dim(R′,R′)][Rh(CO)₂Cl₂] which have been characterized by elemental analyses, electrical conductivity, ¹H-NMR and electronic and IR spectroscopy. Some of these complexes must involve some kind of metal-metal interaction. The complex [Rh(CO)₂Cl.c-Hex-dim(H,H)] has been obtained by reaction of [Rh(CO)₂Cl]₂ with the c-Hex-dim(H,H) ligand in 1:1 Rh/R-dim ratio. The reactions between [(CO)₂Rh.R-dim(H,H)][Rh(CO)₂Cl₂](R = c-Hex or p-C₆H₄OCH₃) with the dppe ligand have been studied. The known complex RhCl(CO)(PPh₃)₂ has been isolated from the reaction of [(CO)₂Rh.R-dim(H,H)]-[Rh(CO)₂Cl₂] (R = c-Hex or p-C₆H₄OCH₃) with PPh₃ ligand.     

Metallorganische verbindungen des 1,2-diethinylbenzols vom typ o-C6H4(CCMR3)2 (M = Si,Ge, Pb)

The preparation of the compounds o-C₆H₄(CCMR₃)₂ (M = Si, Ge, Pb; R = CH₃; M = Pb; R = C₆H₅) is described. Their properties are compared with those of o-C₆H₄(CCSnR₃)₂ (R = CH₃, C₆H₅) and those of their p-isomers. The structures and bonding conditions proposed for these molecules are supported by dipole measurements, mass spectroscopy, IR, Raman, ¹H NMR and ¹³C NMR data.     

Kinetische und mechanistische untersuchungen von übergangsmetallkomplexreaktionen : II. Kinetik und mechanismus der reaktion von trans- bromo(tetracarbonyl)phenylcarbinwolfram mit tertiären arylphosphanen, -arsanen und -stibanen

The kinetics of the reaction of trans-bromo(tetracarbonyl)phenylcarbyne-tungsten (IIIb) with N = PPh₃, AsPh₃, SbPh₃, P(p-C₆H₄CH₃)₃, P(p-C₆H₄Cl)₃, P(p-C₆H₄F)₃, P(p-C₆H₄NMe₂)₃, Ph₂AsCH₂AsPh₂ and P(OPh)₃ have been studied in octane, n-butyl bromide, 1,1,2-trichloroethane and various other solvents. The formation of the monosubstituted carbyne complex follows a first-order rate law. The rates of reaction depend neither on the nature of the substitting nucleophile nor on its concentration. The rates decrease with increasing polarity of the solvent. Under high CO-pressure the substitution is partially reversible. The activation parameters are ΔH^≠ 98–108 kJ mol^?1 and ΔS^≠ 26–53 J K^?1 mol^?1. The results are discussed on the basis of a dissociative mechanism.     

The synthesis of some bidentate bismuth-containing ligands

The synthesis and properties including mass spectra of (o-diphenylphosphinophenyl)diphenylbismuthine, o-C₆H₄(PPh₂)(BiPh₂) and (o-diphenylarsinophenyl)-diphenylbismuthine, o-C₆H₄(AsPh₂)(BiPh₂) are described. The failure of attempts to prepare α, ω-bis(disphenylbismuthino)alkanes is discussed.     

New η-allyl η-cyclopentadienylcobalt cations

[Co(R-η-C₃H₄)(η-C₅H₅)I] is a good precursor for the preparation of some new cationic complexes as the iodide can easily be replaced; thus addition of PEt₃ to the iodo-complex (R  H) gives [Co(η-C₃H₅)(η-C₅H₅)(PEt₃)]⁺. The reactions of [Co(R-η-C₃H₄)(η-C₅H₅))I] (R  H or 2-Me) with AgBF₄ give solutions containing the coordinatively unsaturated species [Co(R-η-C₃H₄)(η-C₅H₅)⁺. The presence of traces of water leads to the formation of [Co(R-ηC₃H₄)-(η-C₅H₅)(H₂O)]⁺. The addition of monodentate ligands L  PEt₃ PPh₃, AsPh₃, SbPh₃, CNCH₃ and bidentate ligands LL  Ph₂PCH₂CH₂PPh₂(dppe) and o-C₆H₄(AsMe₂)₂(diars), gives, respectively mononuclear [Co(2-Me-ηC₃H₄)-(η-C₅H₅)L]⁺ and binuclear ligand-bridged [(2-Me-ηC₃H₄)(η-C₅H₅)CoLLCo(2-Me-ηC₃H₄)(η-C₅H₅))]²⁺ complexes. Crystals of [Co(2-Me-ηC₃H₄)(η-C₅H₅)-(H₂O)]⁺[BF₄]^- are monoclinic, space group P2₁/c, with a 7.858(3), b 10.262(4), c 15.078(4) Å, β 98.36(1)°. The molecular structure contains the cobalt atom bonded to planar 2-Me-allyl and cyclopentadienyl substituents, which are almost parallel with the H₂O molecule in a staggered conformation with respect to the 2-Me group.     

Mechanism of formation of carbene complexes by reaction of cis-[PdCl2(PPh3)(CNR)] with secondary amines

A kinetic study is reported for the reactions of secondary aromatic amines p-YC₆H₄NHR (Y = MeO, Me, H; R = Me, Et) with the isocyanide complexes cis-[PdCl₂(p-XC₆H₄NC)(PPh₃)] (X = Me, H, Cl) leading to the carbene derivatives cis-[PdCl₂ {C(NH-p-C₆H₄X)NR-p-C₆H₄Y} (PPh₃)] in 1,2-dichloroethane at 25°C. A stepwise mechanism is proposed which involves a direct nucleophilic attack of the entering amine on the isocyanide carbon followed by proton transfers to the final carbene complexes. These take place both intramolecularly in a four-membered cyclic transition state and by the agency of one further amine molecule serving as a proton acceptor-donor in a six-membered transition state. Competition experiments with primary amines and trends in rate parameters are discussed to support the mechanism.     

Synthesis of cationic dialkylgold(III) complexes: nature of the facile reductive elimination of alkane

A series of gold(III) cations of the type cis-[CH₃)₂AuL₂]⁺ X^? where L  Ph₃, PMePh₂, PMe₂Ph, PMe₃, AsPh₃, AsPh₃, SbPh₃, $\text{1}\text{2}$H₂NCH₂CH₂NH₂, $\text{1}\text{2}$ Ph₂PCH₂CH₂-PPh₂, $\text{1}\text{2}$ Ph₂AsCH₂CH₂AsPh₂, and $\text{1}\text{2}$o-C₆H₄(AsMe₂)₂ and X  BF₄^?, PF₆^?, ClO₄^?, and F₃CSO₃^? has been prepared. In addition, the cis complexes [(CH₃)(CD₃)-Au(PPh₃)₂]F₃CSO₃, [(C₂H₅)₂Au(PPh₃)₂]F₃CSO and [(n-C₄H₉)₂Au(PPh₃)₂]F₃-CSO₃ have been synthesized. All have been characterized by PMR, Raman and infrared spectroscopy. These [R₂AuL₂]X compounds yield only ethane, butane, or octane via reductive elimination, and no disproportionation is observed. The alkane eliminations have been studied in CHCl₃, CH₃Cl₂, and CH₃COCH₃ solution as a function of temperature, concentration of the complex, and concentration of added ligand L. Elimination is fastest when L is bulky (PPh₃ > PMePh₂ > PMe₂Ph > PMe₃), decreases in the sequence SbPh₃ > AsPh₃ > PPh₃, is slow with chelating ligands, is inhibited by excess ligand, and there is small anion effect as X is varied. As R is varied, the rate of elimination decreases Bu ? Et > Me. An intramolecular dissociative mechanism is proposed which involves rapid elimination of alkane from an electron deficient dialkylgold(III) complex with nonequivalent gold—carbon bonds and produces the corresponding [AuL₂]X complex.     

On the reactivity of platina‐β‐diketones: a straightforward synthesis of trans‐acetylchlorobis(phosphine)platinum(II) complexes and their reactivity

The platina‐β‐diketone [Pt₂{(COMe)₂H}₂(µ‐Cl)₂] ( 1 ) was found to react with monodentate phosphines to yield acetyl(chloro)platinum(II) complexes trans‐[Pt(COMe)Cl(PR₃)₂] (PR₃ = PPh₃, 2a ; P(4‐FC₆H₄)₃, 2b ; PMePh₂, 2c ; PMe₂Ph, 2d ; P(n‐Bu)₃, 2e ; P(o‐tol)₃, 2f ; P(m‐tol)₃, 2g ; P(p‐tol)₃, 2h ). In the reaction with P(o‐tol)₃ the methyl(carbonyl)platinum(II) complex [Pt(Me)Cl(CO){P(o‐tol)₃}] ( 3a ) was found to be an intermediate. On the other hand, treating 1 with P(C₆F₅)₃ led to the formation of [Pt(Me)Cl(CO){P(C₆F₅)₃}] ( 3b ), even in excess of the phosphine. Phosphine ligands with a lower donor capability in complexes 2 and the arsine ligand in trans‐[Pt(COMe)Cl(AsPh₃)₂] ( 2i ) proved to be subject to substitution by stronger donating phosphine ligands, thus forming complexes trans‐[Pt(COMe)Cl(L)L′] (L/L′ = AsPh₃/PPh₃, 4a ; PPh₃/P(n‐Bu)₃, 4b ) and cis‐[Pt(COMe)Cl(dppe)] ( 4c ). Furthermore, in boiling benzene, complexes 2a – 2c and 2i underwent decarbonylation yielding quantitatively methyl(chloro)platinum(II) complexes trans‐[Pt(Me)Cl(L)₂] (L = PPh₃, 5a ; P(4‐FC₆H₄)₃, 5b ; PMePh₂, 5c ; AsPh₃, 5d ). The identities of all complexes were confirmed by ¹H, ¹³C and ³¹P NMR spectroscopy. Single‐crystal X‐ray diffraction analyses of 2a ·2CHCl₃, 2f and 5b showed that the platinum atom is square‐planar coordinated by two phosphine ligands (PPh₃, 2a ; P(o‐tol)₃, 2f ; P(4F‐C₆H₄)₃, 5b ) in mutual trans position as well as by an acetyl ligand ( 2a, 2f ) and a methyl ligand ( 5b ), respectively, trans to a chloro ligand. Single‐crystal X‐ray diffraction analysis of 3b exhibited a square‐planar platinum complex with the two π‐acceptor ligands CO and P(C₆F₅)₃ in mutual cis position (configuration index: SP‐4‐3). Copyright © 2005 John Wiley & Sons, Ltd.     

Studies of lambert's reaction: The formation of [Mn2(CO)8(μ-AsR2)2] complexes from tertiary arsines and [Mn2(CO)10] at high temperatures

Although very bulky ligands e.g.(o-MeC₆H₄)₃E or (μ-C₁₀H₇)₃E (E = P or As) are inert, the normal photochemical or thermal reaction of tertiary phosphines or arsines, L, with [Mn₂(CO)₁₀] is CO substitution with the formation of [Mn₂(CO)₈(L)₂] derivatives (I). At elevated temperatures some triarylarsines, R₃As, undergo Lambert's reaction with ligand fragmentation to give [Mn₂(CO)₈(μ-AsR₂)₂] complexes (II) (R = Ph, p-MeOC₆H₄, p-FC₆H₄, or p-CIC₆H₄) even though, in the absence of [Mn₂(CO)₁₀] R₃As are stable under the same conditions. Exceptional behaviour is exhibited by (p-Me₂NC₆H₄)_3- As which forms a product of type I; by some HN(C₆H₄)₂AsR which give a product of type II as a result of loss of the non-aryl groups R = PhCH₂, cyclo-C₆H₁₁, or MeO; and by Ph(α-C₁₀H₇₂P which is the only phosphine to form a product of type II, albeit in trace amounts only. The thermal decomposition of a n-butanol solution of [Mn₂(CO)₈(AsPh₃)₂] in a sealed tube gives C₆H₆ and [Mn₂(CO)₈(α-AsPh₂)₂], whilst in an open system in the presence of various tertiary phosphines, L, [Mn(H)(CO)₃(L)₂] are obtained. It is suggested that Lambert's reaction is a thermal fragmentation of [Mn(CO)₄(AsR₃]^* radicals, the first to be recognised. They lose the radical R^* which abstracts hydrogen from the solvent. The resulting [Mn(CO)₄(AsR₂)] moiety dimerises to [Mn₂(CO)_8-(α-AsR₂)₂]. the reaction is facilitated by the stability of the departing radical (e.g. PhCH₂ or MeO) and, as the crowding about As is relieved, by its size (e.g. Ph, cyclo-C₆H₁₁, o-MeC₆H₄, or α-C₁₀H₇). In general, phosphine-substituted radicals [Mn(CO)₄(PR)₃]^* do not undergo this decomposition, probably because the PC bonds are much stronger than AsC.     

Cyclometallation reactions of N-(benzylidene)benzylamines with palladium compounds

The cyclometallation of p-RC₆H₄CHNCH₂C₆H₂, (R = H, Cl, NO₂) by PdX₂ (X = Cl, AcO) has been studied.In every case the cyclometallation occurs with formation of a five-membered ring containing the methine group. The structure of these compounds [$\text{PdX(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{CHN}$CH₂C₆H₅)]₂, derived from ¹H NMR spectra, are different from those reported previously. Reaction of these compounds with PEt₃ gives the compounds [PdX(p-RC₆H₃CHNCH₂C₆H₅)(PEt₃)₂] but with an excess of PPh₃ only the complexes [$\text{PdX(}\text{p}\text{-RC}{}_6\text{H}{}_3\text{CHN}$CH₂C₆H₅)(PPh₃)] are formed.     

Reactions of 1,4-diaza-3-methylbutadien-2-ylpalladium(II) derivatives with chloro-bridged rhodium(I) complexes

The reactions of the organometallic 1,4-diazabutadienes, RN=C(R′)C(Me)=NR″ [R = R″ = p-C₆H₄OMe, R′ = trans-PdCl(PPh₃)₂ (DAB); R = p-C₆H₄OMe, R″ = Me, R′ = trans-PdCl(PPh₃)₂ (DAB^I; R = R″ = p-C₆H₄OMe, R′ = Pd(dmtc)-(PPh₃), dmtc = dimethyldithiocarbamate (DAB^II); R = R″ = p-C₆H₄OMe, R′ = PdCl(diphos), diphos = 1,2-bis(diphenylphosphino)ethane (DAB^III)] with [RhCl(COD)]₂ (COD = 1,5-cyclooctadiene, Pd/Rh ratio = $\text{1}\text{2}$) depend on the nature of the ancillary ligands at the Pd atom in group R′. In the reactions with DAB and DAB^I transfer of one PPh₃ ligand from Pd to Rh occurs yielding [RhCl(COD)(PPh₃)] and the new binuclear complexes [Rh(COD) {RN=C(R?)-C(Me)=NR″}], in which the diazabutadiene moiety acts as a chelating bidentate ligand. Exchange of ligands between the two different metallic centers also occurs in the reaction with DAB^II. In this case, the migration of the bidentate dmtc anion yields [Rh(COD)Pdmtc] and [Rh(COD) {RN=C(R?)C(Me)=NR″}]. In contrast, the reaction with DAB^III leads to the ionic product [Rh(COD)- (DAB^III)][RhCl₂(COD)], with no transfer of ligands. The cationic complex [Rh(COD)(DAB^III)]⁺ can be isolated as the perchlorate salt from the same reaction (Pd/Rh ratio = 1/1) in the presence of an excess of NaClO₄. In all the binuclear complexes the coordinated 1,5-cyclooctadiene can be readily displaced by carbon monoxide to give the corresponding dicarbonyl derivatives. The reaction of [RhCl(CO)₂]₂ with DAB and/or DAB^I yields trinuclear complexes of the type [RhCl(CO)₂]₂(DAB), in which the diazabutadiene group acts as a bridging bidentate ligand. Some reactions of the organic diazabutadiene RN=C(Me)C(Me)=NR (R = p-C₆H₄OMe) are also reported for comparison.