Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part V. Polysubstituted derivatives of [Ir4(CO)12]

The dynamic behaviour of twelve polysubstituted derivatives of [Ir₄(CO)₁₂] has been investigated in solution, using 2D-EXSY, and VT-³¹P- and ¹³C-NMR. [Ir₄(CO)₆(μ₂-CO)₃(η⁴-diarsine) PPh₃] and [Ir₄(CO)₆(μ₂-CO)₃(η⁴-nor-bornadiene)(PMePh₂)] exhibit two isomeric forms in solution, which interconvert through an intramolecular change of basal face. The related cluster [Ir₄(CO)₆(μ₂-CO)₃(η⁴-norbornadiene)PPh₃] exists as a single isomer in solution. It displays rotation of CO ligands about the apical Ir-atom, followed by two consecutive changes of basal face. The tetrasubstituted clusters with two chelating ligands [Ir₄(CO)₅(μ₂-CO)₃(η⁴-diolefin)₂] also exhibit rotation of apical CO's, the activation energy increases with greater steric hindrance of the radical ligands. A quantitative analysis of the ³¹P- and ¹³C-2D-EXSY spectra followed by simulation of the corresponding VT-NMR spectra of [IR₄(CO)₅(μ₂-CO)₃(μ₂-L)₂] (L = bis(diphenylphosphino)methane and 1,3-bis(diphenylphosphino)propane) revealed a pairwise averaging of the P-atoms, caused by two parallel changes of basal face averaging all CO ligands. In addition, the restricted rotation of ligands about the apical Ir-atom was identified at higher temperatures. The remaining clusters are either rigid on the NMR time scale, or display CO-scrambling about a single Ir-atom.     

Synthesis,Reactivity, and Fluxional Behaviour of [Ir2Rh2(CO)12], and Crystal Structure of [Ir2Rh2(CO)8(norbornadiene)2]

The synthesis of [Ir₂Rh₂(CO)₁₂] ( 1 ) by the literature method gives a mixture 1 /[IrRh₃(CO)₁₂] which cannot be separated using chromatography. The reaction of [Ir(CO)₄]^? with 1 mol-equiv. of [Rh(CO)₂(THF)₂]⁺ in THF gives pure 1 in 61% yield. Crystals of 1 are highly disordered, unlike those of its derivative [Ir₂Rh₂(CO)₅(μ₂-CO)₃(norbornadiene)₂] which were analysed using X-ray diffraction. The ground-state geometry of 1 in solution has three edge-bridging CO's on the basal IrRh₂ face of the metal tetrahedron. Time averaging of CO's takes place above 230 K. The CO site exchange of lowest activation energy is due to one synchronous change of basal face, as shown by 2D- and VT-¹³C-NMR. Substitution of CO by X^? in 1 takes place at a Rh-atom giving [Ir₂Rh₂(CO)₈(μ₂-CO)₃X]^? (X = Br, I). Substitution by bidentate ligands gives [Ir₂Rh₂(CO)₇(μ₂-CO)₃(η⁴-L)] (L = norbornadiene, cycloocta-1,5-diene) where the ligand L is chelating a Rh-atom of the basal IrRh₂ face. Carbonyl substitution by tridentate ligands gives [Ir₂Rh₂(CO)₆(μ₂-CO)₃(μ₃-L)] (L = 1,3,5-trithiane, tripod) with L capping the triangular basal face of the metal tetrahedron. Carbonyl scrambling is also observed in these substituted derivatives of 1 and is mainly due to the rotation of three terminal CO's about a local C₃ axis on the apical Ir-atom.     

A synthetic route to heteronuclear clusters containing iridium and rhodium: X-ray crystal structures of [IrOs3(μ-H)2(μ-Cl)(CO)12] and [Ir2Rh2(μ-CO)(μ3-CO)2(CO)4(η-C5Me5)2]

The iridium and rhodium complexes [MCl(CO)₂(NH₂C₆H₄Me-4)] (M = Ir or Rh) react with [Os₃(μ-H)₂(CO)₁₀] to give the tetranuclear clusters [MOs₃(μ-H)₂(μ-Cl)(CO)₁₂]; the iridium compound being structurally identified by X-ray diffraction. Similarly, [IrCl(CO)₂(NH₂C₆H₄Me-4)] and [Rh₂(μ-CO)₂(η-C₅Me₅)₂] afford the tetranuclear cluster [Ir₂Rh₂(μ-CO)(μ₃-CO)₂(CO)₄(η-C₅Me₅)₂], also characterised by single-crystal X-ray crystallog     

Variable-Temperature and -Pressure 31P-NMR Study of the Intramolecular PPh3 Migration in the Cluster Compound [Ir2Rh2(CO)11PPh3]

The reaction of [Ir₂Rh₂(CO)₁₂] with 1 mol-equiv. of PPh₃ yields [Ir₂Rh₂(CO)₁₁PPh₃] ( 1 ) as a mixture of two isomers with the phosphine ligand axially bound either to one basal Rh-atom in the kinetically preferred isomer 1 R or to one basal Ir-atom in the thermodynamically preferred isomer 11 . Both isomers are fluxional on the ¹³C-NMR time scale at low temperature due to CO scrambling. Around room temperature, a new type of fluxional process starts to operate which is responsible for the isomerisation 1R?11 , i.e. the intramolecular migration of the reputedly inert PPh₃ ligand from one metal centre to another. The activation volumes of conversions 1R → 11 and 11 → 1R are both positive, indicating that the migration of PPh₃ is dissociative in character. This article reports the first application of variable pressure ³¹P-NMR to mechanistic studies.     

Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part IV. Derivatives with monodentate ligands and edge-bridging bidentate ligands

The fluxionality of [Ir₄(CO)₈(μ₂-CO)₃L] (L = Br^?, I^?, SCN^?, NO₂^?, P(4-ClC₆H₄)₃, PPh₃, P(4-MeOC₆H₄)₃, P(4-Me₂NC₆H₄)₃), as studied by 2D-¹³C-NMR in solution, is due to two successive scrambling processes: the merry-go-round of six basal CO's and CO bridging to alternative faces of the Ir₄ tetrahedron. The basicity of the ligand L has no significant effect on the activation parameters. The scrambling process of lowest activation energy in [Ir₄(CO)₇(μ₂-CO)₃(PMePh₂)₂] correspond to the two possible synchronous CO bridging about a unique face of the metal tetrahedron swapping the relative axial and radial positions of the ligands L. The disubstituted clusters [Ir₄(CO)₁₀(μ₂-L? L)] with one edge-bridging ligand have a ground-state geometry with three edge-bridging CO's (L? L = bis(diphenylphosphino)methane, bis(diphenylarsino)methane, bis(diphenylphosphino)propane) or with all terminal CO's (L? L = CH₃SCH₂SCH₃). In all cases, the fluxional process of lowest activation energy in the merry-go-round of six CO's about a unique triangular face. For the P and As donor ligands, this process is followed by the rotation of terminal CO's bonded to two Ir-atoms residing on the mirror plane of the unbridged intermediate.     

Reactions of cationic rhodium(I) carbonyl compounds with nucleophiles to form alkoxo,carboalkoxy and carboxylato complexes. Part II

Summary The rhodium(I) carbonyl compounds [Rh(CO)L₂2] [BF₄]. 1/2CH₂Cl_nn2 (L = PPh₂ or AsPh₃) react with the nucleophiles OMe⁻, RCOO⁻ (R = Me, Et) under nitrogen to form [Rh(OR)(CO)L₂] (1)–(2) and [Rh(OOCR)(CO)L₂] (7)–(₁₀), respectively. Addition of [Rh(CO)₂(PPh₃)₂]-[BF ₄] to OMe⁻ under nitrogen produces [Rh(COOMe)-(CO) (PPh₃)₂]-MeOH (3), whilst reactions of [Rh(CO)-(PPh₃)₂] [BF₄]·1/2CH₂Cl₂ and [Rh(CO)₂(PPh₃)₂] [BF₄] with OR_- (R = Me, Et or n-Pr) in the presence of CO produce [Rh(COOR)(CO)₂(PPh₃)₂] (4)–(6). The products have been characterised by i.r., ¹H, ³¹P, ¹³Cn.m.r. spectroscopy and elemental analysis.     

[RhCl(CO)(PPh3)]2. A precursor for the synthesis of cationic rhodium complexes with nitrogen donor ligands

Summary The use of [RhCl(CO)(PPh₃)]₂ as a precursor for the synthesis of complexes of the types [Rh(CO)L₂(PPh₃)]A (A = [ClO₄]^– or [BPh₄]^–; L = pyridine type ligand) and [Rh(CO)(L-L)(PPh₃)]A (A = [ClO₄]^– or [BPh₄]^–; L-L = bidentate nitrogen donor) and the preparation of several complexes of the types [Rh(CO)L(PPh₃){P(p-RC₆H₄)₃}]BPh₄ and [Rh(CO)(phen)(PPh₃){P(p-RC₆H₄)₃}]A (A = [ClO₄]^– or [BPh₄]^–; R = H or Me) is described.Author to whom all correspondence should be directed.     

Conversion of allene into μ-dimethylcarbene at a diruthenium centre

Treatment of [Ru₂(CO)(μ-CO) {μ-C(O)C₂Ph₂} (η-C ₅H₅)₂] with allene in toluene at 100°C displaces diphenylacetylene and produces [Ru(CO)(η-C₅H₅)-{η³-C₃H₄Ru(CO)₂(η-C₅H₅)}]; upon protonation a 1-methylvinyl cation [Ru₂(CO)₂(μ-CO){μ-C(Me)CH₂}(η-C₅H₅)₂]⁺ is formed which undergoes nucleophillic attack by hydride to yield the μ-dimethylcarbene complex [Ru₂(CO)₂-(μ-CO)(μ-CMe₂)(η-C₅H₅)₂].     

Coordination chemistry of the [Pt2(μ-S)2(PPh3)4] metalloligand with π-hydrocarbon derivatives of d ruthenium(II), osmium(II), rhodium(III) and iridium(III)

The reactivity of [Pt₂(μ-S)₂(PPh₃)₄] towards [RuCl₂(η⁶-arene)]₂ (arene=C₆H₆, C₆Me₆, p-MeC₆H₄Prⁱ=p-cymene), [OsCl₂(η⁶-p-cymene)]₂ and [MCl₂(η⁵-C₅Me₅)]₂ (M=Rh, Ir) have been probed using electrospray ionisation mass spectrometry. In all cases, dicationic products of the type [Pt₂(μ-S)₂(PPh₃)₄ML]²⁺ (L=π-hydrocarbon ligand) are observed, and a number of complexes have been prepared on the synthetic scale, isolated as their BPh₄⁻ or PF₆⁻ salts, and fully characterised. A single-crystal X-ray structure determination on the Ru p-cymene derivative confirms the presence of a pseudo-five-coordinate Ru centre. This resists addition of small donor ligands such as CO and pyridine. The reaction of [Pt₂(μ-S)₂(PPh₃)₄] with RuClCp(PPh₃)₂ (Cp=η⁵-C₅H₅) gives [Pt₂(μ-S)₂(PPh₃)₄RuCp]⁺. In addition, the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with the related carbonyl complex [RuCl₂(CO)₃]₂, monitored by electrospray mass spectrometry, gives [Pt₂(μ-S)₂(PPh₃)₄Ru(CO)₃Cl]⁺.     

Tetrairidium carbonyl clusters of mono- and di-olefins

The reactions of NEt₄ [Ir₄(CO)₁₁ Br] (I) with mono- and di-olefins in the presence of AgBF₄ gave high yields ( > 90%) of Ir₄(CO)₁₁ (olefin) (II) and Ir4(CO)₁₀(η⁴-diolefin) (III). Oxidation of Ir₄(CO)₁₁ (L = PPh₃, AsPh₃) in the presence of an excess of diolefin by 1 eq. ON(CH₃)₃ gave the clusters Ir₄(CO)₉L(η⁴-diolefin) (IV) and Ir₄(CO)₇L(η⁴-diolefin)₂ (V). Sulphur dioxide quantitatively displaces the monoolefin ligand from II to give Ir₄(CO)₉(μ₂-CO)₂(μ₂-SO₂), which is the first example of a tetrairidium- SO₂ cluster.     

Preparation and Characterization of an Unusual Di-Cobalt Complex; X-Ray Crystal Structure of Co(CO)2(μ-CO)(μ:η2,η4-C4Ph4)Co(CO)2(PPh3)

Reaction of [MoCo(CO)₅(PPh₃)₂(η⁵-C₅H₅)] (1) with diphenylacetylene in tetrahydrofuran at 50 °C yielded two heterobimetallic compounds, [MoCo(CO)₄.(PPh₃){μ-PhC ? CPh}(η⁵-C₅H₅)] (4) and [MoCo(CO)₅{μ-PhC ? CPh} (η⁵-C₅H₅)] (5). However, an unexpected product, Co(CO)₂(μ-CO)(μ:η₂,η⁴-C₄Ph₄)Co(CO)₂(PPh₃) (6), was observed while attempting to grow the crystals for structural determination of 4. The X-ray crystal structure of 6 was determined: triclinic, $ {\rm P}\bar 1 $, a = 11.654(2) Å, b = 12.864(2) Å, c = 13.854(2) Å, α = 89.67(2)°, β = 86.00(2)°, γ= 83.33(2)°, V = 2057.9(6) ų Z=2. In 6, two cobalt fragments are at apical and basal positions of the pseudo-pentagonal pyramidal structure, respectively. The electron count for the apical cobalt fragments is 20, which is rather unusual. It is believed that 6 was formed after the fragmentation and recombination of the fragmented species of 4.     

Synthesis,stability and reactivity of cationic carbonyl complexes of rhodium(I)

Summary Trans-[RhCl(CO)L₂] (L = PPh₃, AsPh₃ or PCy₃) react with AgBF₄ in CH₂Cl₂ to give the novel species [Rh-(CO)L₂]⁺ [BF₄]^–.nCH₂Cl₂ (n = 1/2 or 1 1/2) (1–3), which we believe to be stabilised by weak solvent interaction. The corresponding stibine compound cannot be isolated by the same process, instead [Rh(CO)₂(SbPh₃)₃]⁺ [BF₄]^– (7) is formed when the reaction is carried out in the presence of CO. When reactions designed to prepare [Rh(CO)L₂]⁺ [BF₄]^– are performed in the presence of CO, or [Rh(CO)L₂]⁺ [BF₄]^– complexes are reacted with CO, [Rh(CO)₂L₂]⁺ [BF₄]^– (L = PPh₃, AsPh₃ or PCy₃) (4–6) are formed. If Me₂CO is used as solvent in the preparation of [Rh(CO)L₂]⁺ [BF₄]^– (L = PPh₃ or AsPh₃), then the products are the four-coordinate [Rh(CO)L₂-(Me₂CO)]⁺ [BF₄]^– (8,9) species. The complexes have been characterised by i.r., ³¹P and ¹H n.m.r. spectroscopy and elemental analyses.     

Intramolecular Dynamics of Tetranuclear Carbonyliridium Cluster Compounds. Part II. Disubstituted complexes with one chelating ligand. Crystal structure of [Ir4(CO)7(μ-CO)3(1,5-cyclooctadiene)]

The two complexes [Ir₄(CO)₁₀(diarsine)] (1) and [Ir₄(CO)₁₀(1,5-cyclooctadiene)] (2) bear a bidentate ligand chelating one metal atom of the basal face of the Ir₄ tetrahedron. However, they differ in fluxional behaviour as observed by 2D-exchange and variable-temperature ¹³C-NMR. The CO-site exchange with lowest activation energy proceeds via an unbridged intermediate in 2 , whereas that in 1 occurs via a concerted edge-bridging of CO's to an alternative face of the metal core. This difference is apparently related to different ground-state geometries: the basal CO's are symmetrically bridging in 2 , whereas two CO's are semi-bridging in 1 . The molecular structure of 2 was determined by single crystal X-ray diffractometry. The crystals are orthorhombic, space group Pbca, a = 11.651(4), b = 13.118(3), c = 28.64(1)Å. The idealized molecular symmetry is C_s. The diolefin chelates a basal Ir-atom replacing an axial and a radial CO group on the tetrahedral metal-atom framework.     

Study of hydroformylation of formaldehyde in the presence of rhodium catalysts byin situ IR spectroscopy and the kinetic technique

Carbonylrhodium complexes formed during hydroformylation of CH₂O from various rhodium precursors were investigated byin situ IR spectroscopy. It was found that under the conditions of the hydroformylation of CH₂O inN,N-dimethylacetamide (DMAA), RhH(CO)(PPh₃)₃, RhCl(CO)(PPh₃)₂, RhCl(PPh₃)₃, RhCl(CO)(PBu₃)₂, and [RhCl(CO)₂]₂ form complex systems that necessarily contain anionic complexes, [Rh(CO)₂L_x(DMAA)_y]^– (L = PPh₃, PBu₃,x = 1 to 2,y = 1 to 0; [Rh(CO)₄]^–). The participation of ionic structures in the hydroformylation of CH₂O, most likely, in the step of the activation of CH₂O, was proven by kinetic techniques.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1066–1069, June, 1995.     

Carbonylrhodium complexes with pyridylphosphines: [Rh(chel)(CO)(PPhxpyl3−x)]

Summary Diphenyl(2-pyridyl)phosphine (PPh₂pyl), phenylbis(2-pyridyl)-phosphine (PPhpyl₂) and tris(2-pyridyl)-phosphine (Ppyl₃) react with [Rh(acac)(CO)₂] (acac=acetylacetonate) and Rh(8-oxy)(CO)₂(8-oxy=8-hydroxyquinolinate) yielding [Rh(chel)(CO)(PPh_xpyl_3–x)]. The properties of these complexes were examined by spectral (i.r.,u.v.-vis,³¹P n.m.r.) and chemical methods.     

Platinum,iridium and rhodium complexes with substituted bis-(diphenylphosphino)methane ligands Ph2PCH(R)PPh2 (R = Me,Ph or SiMe3)

Substituted phosphines of the type Ph₂PCH(R)PPh₂ and their Pt^II complexes [PtX₂{Ph₂PCH(R)PPh₂}] (R = Me, Ph or SiMe₃; X = halide) were prepared. Treatment of [PtCl₂(NCBu^t)₂] with Ph₂PCH(SiMe₃)-PPh₂ gave [PtCl₂(Ph₂PCH₂PPh₂)], while treatment with Ph₂PCH(Ph)PPh₂ gave [Pt{Ph₂PCH(Ph)PPh₂}₂]Cl₂. Reaction of p-MeC₆H₄C≡CLi or PhC≡CLi with [PtX₂{Ph₂PCH(Me)PPh₂}] gave [Pt(C≡CC₆H₄Me-p)₂-{Ph₂PCH(Me)PPh₂}] (X = I) and [Pt{Ph₂PC(Me)PPh₂}₂](X = Cl),while reaction of p-MeC₆H₄C≡CLi with [Pt{Ph₂PCH(Ph)PPh₂}₂]Cl₂ gave [Pt{Ph₂PC(Ph)PPh₂}₂]. The platinum complexes [PtMe₂(dpmMe)] or [Pt(CH₂)₄(dpmMe)] fail to undergo ring-opening on treatment with one equivalent of dpmMe [dpmMe = Ph₂PCH(Me)PPh₂]. Treatment of [Ir(CO)Cl(PPh₃)₂] with two equivalents of dpmMe gave [Ir(CO)(dpmMe)₂]Cl. The PF₆ salt was also prepared. Treatment of [Ir(CO)(dpmMe)₂]Cl with [Cu(C≡CPh)₂], [AgCl(PPh₃)] or [AuCl(PPh₃)] failed to give heterobimetallic complexes. Attempts to prepare the dinuclear rhodium complex [Rh₂(CO)₃(μ-Cl)(dpmMe)₂]BPh₄ using a procedure similar to that employed for an analogous dpm (dpm = Ph₂PCH₂PPh₂) complex were unsuccessful. Instead, the mononuclear complex [Rh(CO)(dpmMe)₂]BPh₄ was obtained. The corresponding chloride and PF₆ salts were also prepared. Attempts to prepare [Rh(CO)(dpmMe)₂]Cl in CHCl₃ gave [RhHCl(dpmMe)₂]Cl. Recrystallization of [Rh(CO)(dpmMe)₂]BPh₄ from CHCl₃/EtOH gave [RhO₂(dpmMe)₂]BPh₄. Treatment of [Rh(CO)₂Cl₂]₂ with one equivalent of dpmMe per Rh atom gave two compounds, [Rh(CO)(dpmMe)₂]Cl and a dinuclear complex that undergoes exchange at room temperature between two formulae: [Rh₂(CO)₂(μ-Cl)(μ-CO)(dpmMe)₂]Cl and [Rh₂(CO)₂-(μ-Cl)(dpmMe)₂]Cl. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of homo- and heterodinuclear metal complexes with dimethylsilylene bridged unsymmetrical bis(cyclopentadienyl) ligand

The reaction of the dilithium salt Li₂[Me₂Si(C₅H₄)(C₅Me₄)] (2) of Me₂Si(C₅H₅)(C₅HMe₄) (1) with [MCl(C₈H₁₂)]₂ (M=Rh, Ir) and [RhCl(CO)₂]₂ afforded homodinuclear metal complexes [{Me₂Si(η⁵-C₅H₄)(η⁵-C₅Me₄)}{M(C₈H₁₂)}₂] (M=Rh: 3; M=Ir: 4) and [{Me₂Si(η⁵-C₅H₄)(η⁵-C₅Me₄)}Rh₂(CO)₂(μ-CO)] (5), respectively. The reaction of 2 with RhCl(CO)(PPh₃)₂ afforded a mononuclear metal complex [{Me₂Si(C₅HMe₄)(η⁵-C₅H₄)}Rh(CO)PPh₃] (6) leaving the C₅HMe₄ moiety intact. Taking advantage of the difference in reactivity of the two cyclopentadienyl moieties of 2, heterodinuclear complexes were prepared in one pot. Thus, the reaction of 2 with RhCl(CO)(PPh₃)₂, followed by the treatment with [MCl(C₈H₁₂)]₂ (M=Rh, Ir) afforded a homodinuclear metal complex [Rh(CO)PPh₃{(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}Rh(C₈H₁₂)] (7) consisting of two rhodium centers with different ligands and a heterodinuclear metal complex [Rh(CO)(PPh₃){(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}Ir(C₈H₁₂)] (8). The successive treatment of 2 with [IrCl(C₈H₁₂)]₂ and [RhCl(C₈H₁₂)]₂ provided heterodinuclear metal complex [Ir(C₈H₁₂){(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}Rh(C₈H₁₂)] (9). The reaction of 2 with CoCl(PPh₃)₃ and then with PhCCPh gave a mononuclear cobaltacyclopentadiene complex [{Me₂Si(C₅Me₄H)(η⁵-C₅H₄)}Co(CPhCPhCPhCPh)(PPh₃)] (10). However, successive treatment of 2 with CoCl(PPh₃)₃, PhCCPh and [MCl(C₈H₁₂)]₂ in this order afforded heterodinuclear metal complexes [M(C₈H₁₂){(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}Co(η⁴-C₄Ph₄)] (M=Rh: 11; M=Ir: 12) in which the cobalt center was connected to the C₅Me₄ moiety. Although the heating of 10 afforded a tetraphenylcyclobutadiene complex [{Me₂Si(C₅Me₄H)(η⁵-C₅H₄)}Co(η⁴-C₄Ph₄)] (13), in which the cobalt center was connected to the C₅H₄ moiety, simple heating of the reaction mixture of 2, CoCl(PPh₃)₃ and PhCCPh resulted in the formation of a tetraphenylcyclobutadiene complex [{Me₂Si(C₅H₅)(η⁵-C₅Me₄)}Co(η⁴-C₄Ph₄)] (14), in which the cobalt center was connected to the C₅Me₄ moiety. The mechanism of the cobalt transfer was suggested based on the electrophilicity of the formal trivalent cobaltacyclopentadiene moiety. In the presence of 1,5-cyclooctadiene, the reaction of 2 with CoCl(PPh₃)₃ provided a mononuclear cobalt cyclooctadiene complex [{Me₂Si(C₅Me₄H)(η⁵-C₅H₄)}Co(C₈H₁₂)] (15). The reaction of 15 with n-BuLi followed by the treatment with [MCl(C₈H₁₂)]₂ (M=Rh, Ir) afforded the heterodinuclear metal complexes of [Co(C₈H₁₂){(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}M(C₈H₁₂)] (M=Rh: 16; M=Ir: 17). Treatment of 6 with Fe₂(CO)₉ at room temperature afforded a heterodinuclear metal complex [{Me₂Si(C₅HMe₄)(η⁵-C₅H₄)}{Rh(PPh₃)(μ-CO)₂Fe(CO)₃}] (18) in which the C₅HMe₄ moiety was kept intact. Treatment of dinuclear metal complex 5 with Fe₂(CO)₉ afforded a heterotrinuclear metal complex [{(η⁵-C₅H₄)SiMe₂(η⁵-C₅Me₄)}{Rh(CO)Rh(μ-CO)₂Fe(CO)₃}] (19) having a triangular metal framework. The crystal and molecular structures of 3, 11, 12, 18 and 19 have been determined by single-crystal X-ray diffraction analysis.     

Carbonyl cationic rhodium(I) and iridium(I) complexes with sulphur donor and triphenylphosphine ligands

Summary The reaction of previously reported Rh^I and Ir^I cationic complexes towards carbon monoxide and triphenylphosphine has been studied. Carbonyl rhodium(I) mixed complexes of the formulae [Rh(CO)L₂(PPh₃)]ClO₄, (L=tetrahydrothiophene(tht), trimethylene sulfide(tms), SMe₂, or SEt₂), [(CO)(PPh₃)Rh{-(L-L)}₂Rh(PPh₃)(CO)](ClO₄)₂ (L-L= 2,2,7,7-tetramethyl-3,6-dithiaoctane (tmdto), (MeS)₂(CH₂)₃ (dth), or 1,4-dithiacyclohexane (dt), [Rh(CO)L(PPh₃)₂]ClO₄ (L= tht, tms, SMe₂, or SEt₂), and carbonyl iridium(I) complexes of the formulae [Ir(CO)₂(COD)(PPh₃)]ClO₄, [Ir(CO)(COD)(PPh₃)₂]ClO₄, [(CO)(COD)(PPh₃) Ir{-(L-L)} Ir(PPh₃)(COD)(CO)](ClO₄)₂ (L-L = tmdto or dt), [(CO)₂ (PPh₃)Ir(-tmdto)Ir(PPh₃)(CO)₂](ClO₄)₂, [(CO)₂(PPh₃) Ir(-dt)₂Ir(PPh₃)(CO)₂](ClO₄)₂, were prepared by different synthetic methods.     

Mixed Organometallic–Organic Hybrid Assemblies Based on the Diarsene Complex [Cp2Mo2(CO)4(μ,η2-As2)], AgI Salts and N-Donor Organic Molecules

The reaction of the organometallic diarsene complex [Cp₂Mo₂(CO)₄(η²-As₂)] ( 1 ) with Ag[Al{OC(CF₃)₃}₄] (Ag[TEF]) yielded the Ag^I monomer [Ag(η²- 1 )₃][TEF] ( 2 ). This compound exhibits dynamic behavior in solution, which allows directed selective synthesis of unprecedented organometallic–organic hybrid assemblies upon its reaction with N-donor organic molecules by a stepwise pathway, which is supported by DFT calculations. Accordingly, the reaction of 2 with 2,2′-bipyrimidine ( L1 ) yielded the dicationic molecular compound [{(η²- 1 )₂Ag}₂(μ- L1 )][TEF]₂ ( 3 ) or the 1D polymer [{(η²- 1 )Ag}(μ- L1 )]_n[TEF]_n ( 4 ) depending on the ratio of the reactants. However, its reactions with the pyridine-based linkers 4,4′-bipyridine ( L2 ), 1,2-bis(4-pyridyl)ethylene ( L3 ) and 1,2-bis(4-pyridyl)ethyne ( L4 ) allowed the formation of the 2D polymers [{(η²- 1 )Ag}₂(μ- Lx )₃]_n[TEF]_2n [ Lx=L2 ( 5 ), L3 ( 6 ), L4 ( 7 ), respectively]. Additionally, this concept was extended to step-by-step one-pot reactions of 1 , [Ag(CH₃CN)₃][Al{OC(CF₃)₂(CCl₃)}₄] ([Ag(CH₃CN)₃][TEF^Cl]) and linkers L2 – L4 to produce the 2D polymers [{(η²- 1 )Ag}₂(μ, Lx )₃]_n[TEF^Cl]_2n [ Lx = L2 ( 8 ), L3 ( 9 ), L4 ( 10 ), respectively].     

{μ‐PbSe}: A Heavy CO Homologue as an Unexpected Ligand

Reactions of [K(18‐crown‐6)]₂[Pb₂Se₃] and [K([2.2.2]crypt)]₂[Pb₂Se₃] with [Rh(PPh₃)₃Cl] in en (ethane‐1,2‐diamine) afforded ionic compounds with [Rh₃(PPh₃)₆(μ₃‐Se)₂]^? and [Rh₃(CN)₂(PPh₃)₄(μ₃‐Se)₂(μ‐PbSe)]^3? anions, respectively. The latter contains a PbSe ligand, a rather uncommon homologue of CO that acts as a μ‐bridge between two Rh atoms. Quantum chemical calculations yield a significantly higher bond energy for PbSe than for CO, since the size of the ligand orbitals better matches the comparably rigid Rh‐Se‐Rh angles and the resulting Rh???Rh distance. To rationalize the bent coordination of the ligand, orbitals with significant ligand contributions and their dependence on the bonding angle were investigated in detail.