Reactions of [Os3(CO)10(MeCN)2] with ethynyl thiophenes: The formation of linked clusters

The reaction of 2 equiv. of [Os₃(CO)₁₀(MeCN)₂] with R-CC-L-CC-R (R = H, L = (C₄H₂S); R = SiMe₃, L = (C₄H₂S-C₄H₂S), (C₄H₂S-C₄H₂S-C₄H₂S), (C₄H₂S)-(C₁₄H₈)-(C₄H₂S)) affords the series of linked clusters [{Os₃(CO)₁₀}(HCC(C₄H₂S)CCH){Os₃(CO)₁₀}] (1), [{Os₃(CO)₁₀}(Me₃SiCC(C₄H₂S-C₄H₂S)CCSiMe₃){Os₃(CO)₁₀}] (2), [{Os₃(CO)₁₀}(Me₃SiCC(C₄H₂S-C₄H₂S-C₄H₂S)CCSiMe₃){Os₃(CO)₁₀}] (4) and [{Os₃(CO)₁₀}(Me₃SiCC(C₄H₂S)-(C₁₄H₈)-(C₄H₂S)CCSiMe₃){Os₃(CO)₁₀}] (6) as the major products. The complexes have been characterised by a range of spectroscopic methods and, in the case of 1 and 2 by single crystal X-ray crystallography. The alkyne groups cap the osmium triangles in the expected μ₃-η²-||-bonding mode and each triangle is coordinated by nine terminal and one μ₂-carbonyl group. Solution UV-Vis spectra of the complexes were similar to those observed for the free ligands consistent with there being little delocalisation between the cluster units and the thiophene groups.     

Coordination chemistry of copper-molybdates with alkoxide ligands: The {Mo4O10(OMe)6} and [Mo2O4{RC(CH2O)3}2] clusters as building blocks

The reactions of the Keplerate super cluster [Mo₁₃₂O₃₇₂(CH₃CO₂)₃₀(H₂O)₇₂]⁴²⁻ with a Cu(II) source and an organonitrogen donor in methanol/DMF solutions yielded a series of bimetallic organic-inorganic oxide hybrid materials, including the molecular species [Cu(phen)₂MoO₄] (1) and [{Cu(terpy)}₂(MoO₄)₂] (2) and a series of materials constructed from the tetranuclear building block {Mo₄O₁₀(OMe)₆}²⁻: the molecular [{Cu₂(phen)₂(O₂CCH₃)₂ (MeOH)}Mo₄O₁₀(OMe)₆] (3), [{Cu(terpy)(O₂CCH₃)}₂Mo₄O₁₀(OMe)₆] (4) and [{Cu(terpy)Cl}₂Mo₄O₁₀(OMe)₆] (5), the one-dimensional phases [{Cu(bpy)(HOMe)₂}Mo₄O₁₀(OMe)₆] (6), [{Cu(bpy)(DMF)₂}Mo₄O₁₀(OMe)₆] (7), [{Cu(bpa)(DMF)₂}Mo₄O₁₀(OMe)₆] (8), [{Cu(phen)(DMF)₂}Mo₄O₁₀(OMe)₆] (9) and [{CuCl(dpa)}₂Mo₄O₁₀(OMe)₆] (10), and the two-dimensional material [{Cu₂(DMF)₂(pdpa)}{Mo₄O₁₀(OMe)₆}₂] (11). When methanol is replaced by the tridentate alkoxide tris-methoxypropane (trisp), the {Mo₂O₄(trisp)₂}²⁻ cluster building block is observed for [Cu(phen)Mo₂O₄(trisp)₂] (12), [Cu(bpa)(DMF)Mo₂O₄(trisp)₂] (13) and [{Cu(bpy)(NO₃)}₂Mo₂O₄(trisp)₂] (14).     

Synthesis and characterization of two isomers of Os3(CO)10(C5H4N-2-C(H)NR) and the conversion to ortho-metallated HOs3(C5H3N-2-C(H)NR)(CO)9. Part III. X-ray Structure of HOs3(C5H3N-2-C(H)Ni-Pr)(CO)9

Os₃(CO)₁₀(MeCN)₂ reacts at room temperature in MeCN or toluene with R-Pyca2 to yield two isomers of Os₃(CO)₁₀(R-Pyca) that differ in the bonding of the R-Pyca ligand to the Os₃(CO)₁₀ unit. In all cases Os₃(CO)₁₀(R-Pyca(4e)) (isomer A; 4a: R = c-Pr, 4b: R = i-Pr, 4c: R = neo-Pent, 4d: R = t-Bu), containing a chelating 4e donating R-Pyca ligand and three OsS bonds, could be isolated. In the case of R = c-Pr and R = i-Pr Os₃(CO)₁₀(R-Pyca(6e)) (isomer B; 5a: R = c-Pr, 5b: R = i-Pr), in which only two OsS bonds are present and the R-Pyca ligand is bonded as a 6e donating ligand bridging two non-bonded Os atoms, could be isolated as a minor product.At 70 °C Os₃(CO)₁₀(R-Pyca(4e)) (4b and 4d) loses one carbonyl and the pyridine moiety of the R-Pyca ligand is ortho-metallated to form HOs₃(C₅H₃N-2-C(H)NR)(CO)₉ (6b: R = i-Pr and 6d: R = t-Bu). Under the same conditions Os₃(CO)₁₀(i-Pr-Pyca(6e)) (5b) reacts to Os₂(CO)₆(6e)) (7b) containing a bridging 6e donating ligands. The latter two reactions were followed with FT-IR spectroscopy in a high temperature IR cell.The structure of the complexes in solution have been studied by ¹H and ¹C NMR and IR spectroscopy. The stoichiometries of 4a and 5a were determined by FAB-mass spectrometry while an exact mass determination was carried out for 4a.The crystal structure of 6b has been determined. Crystal of 6b are monoclinic, space group P2₁/n, with a = 7.808(2),b = 17.613(3),c = 16.400(8)Å, β = 94.09(3)° and Z = 4. The structure was refined to R = 0.039. The molecule contains a triangular array of osmium atoms [Os(1)Os(2) = 2.898(2)Å, Os(1)Os(3) = 2.886(2)Åand Os(2)O(3) = 2.911(2)Å] and nine terminally bonded carbonyl ligands. The C₅H₃N-2-C(H)N-i-Pr ligand is chelate bonded to Os(2) with the pyridine and imine nitrogens atoms axially and equatorially coordinated respectively [Os(2)N(1) = 2.00(2)Åand Os(2)N(2) = 2.11(2)Å]. The i-Pr-Pyca ligand is ortho-metallated at C(1) and forms a four membered ring containing Os(2), Os(3), C(1) and N(1), the Os(3)C(1) distance being 2.12(2)Å. The hydride, which could not be located unequivocally from a difference Fourier map is proposed to bridge the Os(2)(3) bond on the basis of stereochemical considerations.     

Syntheses, structures and electrochemical study of π-acetylene complexes of cobalt

The preparation and characterisation of the complexes [Co₂(CO)₄(PMe₃)₂][Co₂(CO)₆](Me₃SiC₂C₂SiMe₃) (4), [Co₂(CO)₄(dppm)][Co₂(CO)₆](Me₃SiC₂C₂H) (5), [Co₂(CO)₄(dppa)][Co₂(CO)₆](Me₃SiC₂C₂SiMe₃) (6), [Co₂(CO)₄(dppm)]₂[Co₂(CO)₆](Me₃SiC₂CCC₂C₂SiMe₃) (7) and [{SiMe₃(Co₂(CO)₄(dppm))C₂}₂(HCC)(1,3,5-C₆H₃)] (8) are described. An electrochemical study of the complexes 5-8 and of the related [Co₂(CO)₄(dppm)]₂(Me₃SiC₂(CC)₂C₂SiMe₃) (1), [Co₂(CO)₄(dppa)]₂(Me₃SiC₂C₂SiMe₃) (2) and [{SiMe₃(Co₂(CO)₄(dppm))C₂}(HCC)₂(1,3,5-C₆H₃)] (3) is presented by means of the cyclic and square-wave voltammetry techniques. Crystals of 8 suitable for single-crystal X-ray diffraction were grown and the molecular structure of this compound is discussed.     

Synthesis of [{Os3(CO)10(μ2-H)}2{μ2,μ2-NC6H4C6H4N}] and [{Os3(CO)9(μ2-H)PPh3}2{μ2,μ2-NC6H4C6H4N}]: Carbon–carbon bond formation promoted by organorhodium species

Synthesis and characterization of linked cluster [{Os₃(CO)₁₀(μ₂-H)}₂{μ₂,μ₂-NC₆H₄C₆H₄N}] (1) from the reaction of [Os₃Rh(μ-H)₃(CO)₁₂] with aniline in the presence of an excess amount of 4-vinyl phenol in refluxing heptane is reported. A similar reaction with [Os₃(CO)₁₀(NCMe)₂] as starting material gave a known compound, [Os₃(CO)₁₀(μ₂-H)(μ₂-HNC₆H₅)] (2). The treatment of complexes 1 and 2 with Wilkinson’s catalyst in refluxing heptane respectively, yielded [{Os₃(CO)₉(μ₂-H)PPh₃}₂{μ₂,μ₂-NC₆H₄C₆H₄N}] (3). An interesting and unexpected C–C coupling of phenyl-amido ligands was observed in complexes 1 and 3, which is believed to be catalysed by the organometallic rhodium species. The newly synthesized compounds 1 and 3 were fully characterized by IR, ¹H NMR spectroscopy, mass spectroscopy, elemental analysis, and X-ray crystallography. Both structures 1 and 3 comprise two triangles of osmium atoms. The two triangular osmium metal cores are linked by a bi-amido ligand via the two nitrogen atoms N(1) and N(1)* and N(1) and N(2), at their equatorial sites. The electronic absorption spectra of complexes 1, 2, and 3 display both low energy absorption, dπ (Os) → π* (amido) metal-to-ligand charge-transfer (MLCT) transition, and π → π* intra-ligand electronic transitions of the amido and bi-amido ligands.     

Reactivity of electron-deficient triosmium quinoline cluster [Os3(CO)9(μ3-η-C9H6N)(μ-H)] with alkynes

Reactions of the electron-deficient triosmium cluster [Os₃(CO)₉(μ₃-η²-C₉H₆N)(μ-H)] (1) with various alkynes are described. Cluster 1 readily reacts with the activated alkyne dimethyl acetylenedicarboxylate (dmad) upon mild heating (65-70 °C) to give the adduct [Os₃(CO)₉(μ-C₉H₆N)(μ₃-MeO₂CCCHCO₂Me)] (2). In contrast, a similar reaction of 1 with diphenylacetylene affords previously reported compounds [Os₃(CO)₁₀(μ-η²-C₉H₆N)(μ-H)] (3), [Os₃(CO)₉(μ-C₄Ph₄)] (4) and [Os₃(CO)₈{μ₃-C(C₆H₄)C₃Ph₃}(μ-H)] (5) while with 2-butyne gives only the known compound [Os₃(CO)₇(μ-C₄Me₄)(μ₃-C₂Me₂)] (6). The new cluster 2 has been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis.     

Synthesis, characterisation and natural abundance Os NMR spectroscopy of hydride bridged triosmium clusters with chiral diphosphine ligands

Treatment of [Os₃(μ-H)₂(CO)₁₀] with the chiral diphosphines BINAP, tolBINAP [(R)-2,2′-bis(di-4-tolylphosphino)-1,1′-binaphthyl], DIOP [(4R,5R)-(−)-O-isopropenylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane] affords [Os₃(μ-H)₂(CO)₈(μ-L)] (L = BINAP (1), tolBINAP (2), DIOP (4)) in high yield. The X-ray structures for 1, 2 and 4 are reported, and structural and spectroscopic comparisons are made between these clusters and [Os₃(μ-H)₂(CO)₈(μ-L)] (L = dppm (5), dppe (6), dppp (7)) which were synthesised similarly. Compounds 5 to 7 were previously synthesised by hydrogenation of 1,2-[Os₃(CO)₁₀(μ-L)] but the route from [Os₃(μ-H)₂(CO)₁₀] is preferable. The H-bridged Os?Os distances are similar in 1, 2 and 4 indicating that these species are formally unsaturated 46-electron clusters. The P?P distances vary from 4.24 to 4.30 Å in 1 and 2, respectively, to 4.53 Å in 4 and there are related changes in the angles associated with the ligand set around the H-bridged osmium atoms. Introduction of the diphosphine ligands completely suppresses the ability to add CO, to insert acetylene to form a μ-η¹,η²-vinyl compound, and to exchange hydride ligands with styrene-d₈, which are reactions characteristic of [Os₃(μ-H)₂(CO)₁₀]. Clusters 2 and 5-7 were also used to examine the potential of natural abundance ¹⁸⁷Os NMR spectroscopy through techniques based on inverse detection by HMQC, HSQC and HMBC spectroscopy.     

A series of thiolato-bridged di- and trinuclear complexes derived from [Tp∗Rh(SPh)2(MeCN)] (Tp∗ = hydrotris(3,5-dimethylpyrazol-1-yl)borate)

Treatment of the Rh(III) complex [Tp∗Rh(SPh)₂(MeCN)] (1) with a series of late transition metal complexes resulted in the formations of thiolate-bridged di- and trinuclear complexes, which include the Rh(III)-Rh(I) complexes, [Tp∗RhCl(μ-SPh)₂Rh(cod)] (2) and [Tp∗RhCl(μ-SPh)₂Rh(PPh₃)₂], the Rh(III)-Pd(II) complexes, [Tp∗RhCl(μ-SPh)₂Pd(η³-C₃H₅)] (4), [{Tp∗Rh(MeCN)}(μ-SPh)₂PdCl₂] (5), and [{Tp∗RhCl(μ-SPh)₂}₂Pd] (6), and the Rh(III)-Pt(II) complex [{Tp∗RhCl(μ-SPh)₂}₂Pt] (7). Early-late transition metal complexes containing the Rh(III)-Re(I) and Rh(III)-Mo(0) metal centers, [Tp∗RhCl(μ-SPh)₂Re(CO)₄] and [{Tp∗Rh(CO)}(μ-SPh)₂Mo(CO)₄] were also prepared from 1. The X-ray analysis has been carried out to confirm the structures for 2, 4, 5, 6, and 7.     

Carbon-hydrogen bond activation of phenyldi(2-thienyl)phosphine at a triosmium cluster centre

The phenyldi(2-thienyl)phosphine (PhPTh₂) complexes [Os₃(CO)_12−n(PhPTh₂)_n] (n = 1-3) (1-3) have been prepared. Thermolysis of 1 and either 2 or 3 in octane affords carbon-hydrogen bond activation products [Os₃(CO)₉{μ₃-PPhTh(C₄H₂S)}(μ-H)] (4) and [Os₃(CO)₈(PPhTh₂){μ₃-PPhTh(C₄H₂S)}(μ-H)] (5), respectively. Both exist as isomeric mixtures differing in the relative positions of phenyl and thienyl substituents with respect to the triosmium centre. The nature of the process has been confirmed by a single crystal X-ray diffraction analysis of 4.     

Synthesis and structure of [{C7F15CO2}2AgAu(PPh3)]2 and its use in electrodeposition of gold-silver alloys

[{C₇F₁₅CO₂}₂AgAu(PPh₃)]₂ is obtained in good yield from the reaction of [C₇F₁₅CO₂Ag] with [ClAuPPh₃] in THF solution. The crystal structure shows a zig-zag Au-Ag-Ag-Au core with fluorocarboxylate ligands bridging the Au-Ag and Ag-Ag bonds and triphenylphosphine groups bound to Au. Electrodeposition from acetonitrile yields Au-Ag alloys. The deposited alloys are Ag rich and the composition varies with deposition potential.     

Coordination polymers of Cu(II) and Cd(II) with bifunctional chelates of the type dipicolylamino-alkylcarboxylate, (NC5H4CH2)2N(CH2)nCO2H (n = 1, 2, 3 and 4)

A series of bifunctional chelates of the type dipicolylamino-alkylcarboxylate (NC₅H₄CH₂)₂N(CH₂)_nCO₂H (n = 1-4; HL¹-HL⁴, respectively) has been prepared. Reactions of the ligands in aqueous methanol/N,N-dimethylformamide with the appropriate Cu(II) salts yielded the compounds [CuL¹](NO₃)·H₂O (1·H₂O), [CuL²(H₂O)]BF₄·H₂O (2·H₂O), [Cu(HL³)(SO₄)]₂ (3) and [CuL⁴(NO₃)]·MeOH (4·MeOH). While compounds 1, 2 and 4 are one-dimensional, the detailed connectivities within the chains are quite distinct, depending on factors such as alkyl chain length and ligation of aqua ligands or anionic components. In contrast to 1, 2 and 4, the structure of 3 is molecular, a binuclear assembly of edge-sharing Cu(II) ‘4+2’ distorted octahedra. The Cd(II) species, [{CdL²}₂(SO₄)]·4H₂O (5·4H₂O), prepared from HL² and CdSO₄·nH₂O in aqueous methanol/N,N-dimethylformamide, is two-dimensional, with a network constructed from binuclear units of seven coordinate Cd(II), , linked through bridging SO₄²⁻ groups to produce an assembly of linked hexagonal rings [{CdL²}₂(SO₄)]₆.     

Interaction of Os3(CO)12 with silica and lanthanum oxide supports

Interaction of Os₃(CO)₁₂ has been studied with SiO₂ and La₂O₃. On SiO₂, a hydridotriosmiumcarbonyl is formed at 50 middot; C. The cluster breaks up at 250 middot; C. On La₂O₃ the osmium cluster breaks up at room temperature forming mononuclear tri- and dicarbonyl osmium species. At 250 middot; C, only the dicarbonyl survives but the tricarbonyl can be regenerated by treatment with CO.     

Acid/amide bonding for anthranilic acid derivatives: crystal structures of [W(X)Cl3(HO2CC6H4NH-2)] (X = O, NPh)

The complexes [W(X)Cl₃(HO₂CC₆H₄NH-2)] [X = O (1), NPh (2)] have been obtained by reaction of either [WOCl₄] or [W(NPh)Cl₄(Et₂O)] with anthranilic acid {1,2-(NH₂)(CO₂H)C₆H₄}, respectively. The X-ray crystal structures reveal pseudo-octahedral metal centres, each with a mer-arrangement of chlorines and a chelating acid/amide ligand derived from anthranilic acid. The acid group of this chelate ligand is trans to either the oxo or organoimido functionality.     

Synthesis of monoamine derivatives of [Ir4(CO)12]. X-ray crystal structure of [Ir4(CO)11(4-picoline)]

The mono-substituted amine derivatives [Ir₄(CO)₁₁L] (L = pyridine (1), 4-methylpyridine (2), 4-ter-butyl pyridine (3), 3,5-dimethylpyridine (4), 3,4-dimethylpyridine (5)) were obtained by the reaction of [Ir₄(CO)₁₁Br]⁻ with the corresponding aromatic amine. In the solid state, cluster 2 has an approximate C_s symmetry with all terminal ligands as shown by an X-ray analysis. In solution, this unbridged structure is in dynamic equilibrium with two other isomeric forms having three edge-bridging CO’s on a common basal face and the amine ligand coordinated in axial or in radial position relative to this face.     

Isolation of [{HB(Me2pz)3}MoO2(OC6H4S)]2, a binuclear Mo(VI) complex containing a disulfide bond

Aerial recrystallization of the mononuclear molybdenum(V) complex {HB(Me₂pz)₃}MoO(OC₆H₄-o-S) produced the novel binuclear Mo(VI) complex [{HB(Me₂pz)₃}MoO₂(OC₆H₄- o-S)]₂ which contains a disulfide bond. The dimer crystallizes as the dioxane solvate in the space group C2/c with cell parameters a=23.46(2), b=11.100(4), c=21.571(8) Å, β=104.23(4)°, Z=4. Final R_w=0.062 (2236 reflections with F_o>3σ(F_o), 301 variable parameters). The dimer contains two crystallographically identical distorted octahedral MoO₂²⁺ centers. One face of each octahedron is occupied by two oxo ligands and a phenolate oxygen atom; the opposite face is occupied by three nitrogens of the HB(Me₂pz)₃⁻ ligand. The two Mo(VI) centers of the dimers are linked by a disulfide bond formed upon oxidation of the 2-mercaptophenolate ligand of the original molybdenum(V) compound.     

Short-bite aminobis(phosphonite) containing olefinic functionalities, PhN{P(OC6H3(OMe-o)(C3H5-p))2}2: Synthesis and transition metal complexes

Short-bite aminobis(phosphonite) containing olefinic functionalities, PhN{P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂ (1) was synthesized by reacting PhN(PCl₂)₂ with eugenol in the presence of triethylamine. The ligand 1 acts as a bidentate chelating ligand toward metal complexes [M(CO)₄(C₅H₁₀NH)₂] forming [M(CO)₄{η²-PhN{P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂}] (M = Mo, 2; W, 3). The reaction between 1 and [CpFe(CO)₂]₂ leads to the cleavage of one of the P-N bonds due to the metal assisted hydrolysis to give a mononuclear complex [CpFe(CO){P(O)(OC₆H₃(OMe-o)(C₃H₅-p))₂}{PhN(H)(P(OC₆H₃(OMe-o)(C₃H₅-p))₂)}] (4). Treatment of 1 with gold(I) derivative, [AuCl(SMe₂)] resulted in the formation of a dinuclear complex, [(AuCl)₂{PhN{P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂}] (5) with a Au···Au distance of 3.118(2) Å indicating the possibility of aurophilic interactions. An equimolar reaction between 1 and [Ru(η⁶-p-cymene)Cl₂]₂ afforded a tri-chloro-bridged bimetallic complex [(η⁶-p-cymene)Ru(μ-Cl)₃Ru{PhN(P(OC₆H₃(OMe-o)(C₃H₅-p))₂)₂}Cl] (6). The crystal structures of 1-3 and 5 were established by single crystal X-ray diffraction studies.     

Dinuclear nickel(II) and zinc(II) complexes of 2,6-bis[{bis(2-pyridylmethyl)amino}methyl]-4-methylphenol

Reaction of the symmetrical proligand H₂L with metal(II) acetate and a counteranion to promote crystallisation has given the homodinuclear complexes [Zn₂L(OAc)₂](BF₄)]·2MeOH and [Ni₂L(OAc)₂](BF₄)]·2MeOH the crystal structures of which are reported. These show the presence of a triply bridging (μ-cresolato)bis(μ-carboxylato) dimetal core.     

Insertion reactions of organic anhydrides and the Cu(I) alkoxide [CuOBu]

The synthesis and structural characterization of the copper salts [Cu₈(benzoate)₈(THF)₆] (1), [Cu₂{(CO₂)₂C₆H₂(Boc)₂}dppm₂]₂ (2) and [Cu₂{(CO₂)₂C₁₀H₄(Boc)₂}dppm₂]₂ (3) [Boc = tert-butoxycarbonyl, dppm = 1,2-bis(diphenylphosphino)methane] prove that cyclic organic anhydrides and dianhydrides readily insert into the Cu-O bond of [CuO^tBu] forming carboxylate ligands with ester functionalities in the ligand periphery. [Mn₃(o-Boc-benzoate)₆(DME)₂] (4) (DME = 1,2-dimethoxyethane) was synthesized by the metathesis reaction of [Cu(I)(o-Boc-benzoate)] with MnCl₂.     

Kinetics of CO substitution in Co4(CO)12 and Rh4(CO)12

The kinetics of rapid CO substitution by PPh₃ in Co₄(CO)₁₂ and Rh₄(CO)₁₂ have been examined by stopped-flow and low temperature FT-IR methods. In Co₄(CO)₁₂ rapid (k_obs ∼ 1.8 s⁻¹) substitution of CO occurs after a 1–15 s induction period at 28 °C in C₆H₅Cl solvent by a catalytic process. Addition of PPh₃ to Rh₄(CO)₁₂ yields Rh₄(CO)₁₁(PPh₃) according to a predominantly second order rate law k₁[Rh₄- (CO)₁₂] + k₂[Rh₄(CO)₁₂][PPh₃] with k₁ = 25 ± 11 s⁻¹ and k₂ = 2.97 ± 0.27 X 10⁴ M⁻¹ s⁻¹ at 28 °C. Substitution of a second CO ligand also occurs rapidly with k₁ = 0.15 ± 0.09 s⁻¹ and k₂ = 6.54 ± 0.07 X 10² M⁻¹ s⁻¹ at 28 °C. The reactivity of Rh₄(CO)₁₂ toward associative substitution is 10⁴– 10¹¹ faster than for the Co and Ir analogues, In Rh₄(CO)₁₁(PPh₃) the increase in CO substitution rates over Co and Rh analogues is 10²–10⁷. The ordering of associative substitution rates Co << Rh >>> Ir in these clusters exaggerates the trend seen in mononuclear metal complexes.     

Synthesis and reactions of [M(CO)4(Ph2PSiMe3)X] complexes (M = Mn,Re; X = Halogen)

The silylphosphine ligand Ph₂PSiMe₃ reacts readily with a slurry of [Re(CO)₅X] (X  Cl, Br) in polar and in non-polar solvents to yield soluble cis-[Re(CO)₄- (Ph₂PSiMe₃)X] (Ia, X  Cl;Ib, X  Br) via CO substitution. Compound I is readily hydrolyzed by water or silica gel to cis-[Re(CO)₄(Ph₂PH)X]. Compound Ib reacts with [Re(CO)₅Br] to yield [Re₂(CO)₈(μ-PPh₂)- (μ-Br)] (II), and with [Mn(CO)₅Br] to yield [MnRe- (CO)₈(μ-PPh₂)(μ-Br)] (III).The reaction of Ph₂PSiMe₃ with [Mn(CO)₅X] (X=Cl,Br,I) is highly dependent upon reaction conditions.In polar and in non-polar solvents, an excess of ligand gives mainly cis-[Mn(CO)₄(Ph₂PSiMe₃)X] (IVa, X  Cl;IVb, X  Br;IVc, X I). With ligand: [Mn(CO)₅X] reacting ratios in the range 0.5–1.0:1, the products from the three respective halomanganese complexes in THF were: (a) mainly [Mn₂(CO)₈(μ- PPh₂)(μ-Cl) (Va); (b) both [Mn(CO)₄(Ph₂PSiMe₃)Br] and [Mn₂(CO)₈(μ-PPh₂)(μ-Br)] (Vb); and (c) exclusively [Mn(CO)₄(Ph₂PSiMe₃)I]. The compounds IVa-c are stable in solution at ambient temperatures and are readily hydrolyzed by water or methanol to [Mn(CO)₄(Ph₂PH)X]. Compound IVb reacts at room temperature with [Mn(CO)₅Cl] to yield only [Mn₂- (CO)₈(μ-PPh₂)(μ-Br)] (Vb); compound IVc reacts in hot toluene with [Mn(CO)₅Cl] to yield mainly [Mn₂(CO)₈(μ-PPh₂)(μ-I)] (Vc), together with a small amount of the chloro-bridged analog.The dinuclear species II, III and Va-c appear to be formed mainly via an intermolecular elimination of Me₃SiX from the appropriate [M(CO)₄(Ph₂PSiMe₃)X] and metalpentacarbonylhalide (chloride or bromide) complexes.