Synthese und Kristallstruktur des ersten Cp*‐geschützten Cobalttelluridclusters: Darstellung von [(Cp*Co)4(μ3‐Te)4] durch milde Oxidation von [Cp*CoCl]2 mittels Li4Sn2Te6 · 8 en

Synthesis and Crystal Structure of the First Known Cp* Ligated Cobalt Telluride Cluster: Mild Oxidation of [Cp*CoCl]₂ by Li₄Sn₂Te₆ · 8 en to give [(Cp*Co)₄(μ₃‐Te)₄] Oxidation of cobalt(II) complex [Cp*CoCl]₂ (Cp* = pentamethylcyclopentadiene) with binary Zintl polyanion hexatellurodistannate(IV) [Sn₂Te₆]^4– in Li₄Sn₂Te₆ · 8 en (en = 1,2‐diaminoethane) leads to the formation of the first Cp* ligated cobalt telluride cluster [(Cp*Co)₄(μ₃‐Te)₄]. The compound crystallizes as black cuboids that are suitable for X‐ray structural analysis. Space group P 1, lattice dimensions at 203 K: a = 1127.9(2), b = 1156.2(3), c = 1882.3(4) pm, α = 83.27(2), β = 83.24(2), γ = 66.11(1)°, V = 2222.3(9) · 10⁶ pm³, R₁ = 0.0681. The molecular structure of the compound features a Co₄Te₄ heterocubane and thus distributes to the completion of the series of known transition metal chalcogenide heterocubanes.     

Synthesen und Strukturen neuer amido- und imidoverbrückter Cobaltcluster: [Li(THF)2]3[Co3(μ2-NHMes)3Cl6] (1), [Li(DME)3]2[Co18(μ4-NPh)3(μ3-NPh)12Cl3] (2), [Li(DME)3]2[Co6(μ4-NPh)(μ2-NPh)6(PPh2Et)2] (3) und [Li(THF)4][Co8(μ3-NPh)6(μ2-NPh)3(PPh3)2] (4)

Syntheses and Crystal Structures of new Amido- und Imidobridged Cobalt Clusters: [Li(THF)₂]₃[Co₃(μ₂-NHMes)₃Cl₆] (1), [Li(DME)₃]₂[Co₁₈(μ₄-NPh)₃(μ₃-NPh)₁₂Cl₃] (2), [Li(DME)₃]₂[Co₆(μ₄-NPh)(μ₂-NPh)₆(PPh₂Et)₂] (3), and [Li(THF)₄][Co₈(μ₃-NPh)₆(μ₂-NPh)₃(PPh₃)₂] (4) The reactions of cobalt(II)-chloride with the lithium-amides LiNHMes and Li₂NPh leads to an amido-bridged multinuclear complex [Li(THF)₂]₃[Co₃(μ₂-NHMes)₃Cl₆] ( 1 ) as well as to the imido-bridged cobalt cluster [Li(DME)₃]₂[Co₁₈(μ₄-NPh)₃(μ₃-NPh)₁₂Cl₃] ( 2 ). In the presence of tertiary phosphines two imido-bridged cobalt clusters [Li(DME)₃]₂[Co₆(μ₄-NPh)(μ₂-NPh)₆(PPh₂Et)₂] ( 3 ) and [Li(THF)₄][Co₈(μ₃-NPh)₆(μ₂-NPh)₃(PPh₃)₂] ( 4 ) result. The structures of 1 – 4 were characterized by X-ray single crystal structure analysis.     

[Hg8(μ‐n‐C3H7Te)12(μ‐Br)Br3] — Synthesis and Structure

The novel mercury‐tellurium cluster [Hg₈(μ‐n‐C₃H₇Te)₁₂(μ₂‐Br)Br₃] is formed during the reaction of HgBr₂ and (n‐C₃H₇Te)₂Hg in DMSO. Its crystal structure has been elucidated showing [Hg₈(μ‐n‐C₃H₇Te)₁₂(μ₂‐Br)]³⁺ units with a bromine‐centered distorted Hg₈ cube. The mercury atoms are bridged by n‐C₃H₇Te^— ligands and the resulting clusters are linked to a three‐dimensional network by bromine atoms. The close packing of the cluster is mainly determined by the flexible n‐propyl residues of the telluride building blocks.     

Synthese und Strukturen neuer selenido‐ und selenolatoverbrückter Kupfercluster: [Cu38Se13(SePh)12(dppb)6] (1), [Cu(dppp)2][Cu25Se4(SePh)18(dppp)2] (2), [Cu36Se5(SePh)26(dppa)4] (3), [Cu58Se16(SePh)24(dppa)6] (4) und [Cu3(SeMes)3(dppm)] (5)

Syntheses and Crystal Structures of new Selenido‐ and Selenolato‐bridged Copper Clusters: [Cu₃₈Se₁₃(SePh)₁₂(dppb)₆] (1), [Cu(dppp)₂][Cu₂₅Se₄(SePh)₁₈(dppp)₂] (2), [Cu₃₆Se₅(SePh)₂₆(dppa)₄] (3), [Cu₅₈Se₁₆(SePh)₂₄(dppa)₆] (4), and [Cu₃(SeMes)₃(dppm)] (5) The reactions of copper(I) chloride or copper(I) acetate with monodentate phosphine ligands (PR₃; R = organic group) and Se(SiMe₃)₂ have already lead to the formation of CuSe clusters with up to 146 copper and 73 selenium atoms. If the starting materials and the bidentate phosphine ligands (Ph₂P–(CH₂)_n–PPh₂, n = 1: dppm, n = 3: dppp, n = 4: dppb; Ph₂P–C≡C–PPh₂: dppa) and silylated chalcogen derivates are changed (RSeSiMe₃; R = Ph, Mes) a series of new CuSe clusters can be synthesized. From single crystal X‐ray structure analysis one can characterise [Cu₃₈Se₁₃(SePh)₁₂(dppb)₆] ( 1 ), [Cu(dppp)₂] · [Cu₂₅Se₄(SePh)₁₈(dppp)₂] ( 2 ), [Cu₃₆Se₅(SePh)₂₆(dppa)₄] ( 3 ), [Cu₅₈Se₁₆(SePh)₂₄(dppa)₆] ( 4 ) and [Cu₃(SeMes)₃(dppm)] ( 5 ). In this new class of CuSe clusters, compounds 1 and 4 possess a spherical cluster skeleton, wheras 2 and 3 have a layered cluster core.     

[(TeMe2)Mn(CO)4(μ5-Te)(μ4-Te)Mn4(CO)12]−: A Pentacoordinate Bridging Tellurido Ligand in a Square-Pyramidal Geometry

The first Te–Mn–CO clusters were obtained by the thermal reaction of K₂TeO₃ with [Mn₂(CO)₁₀] in MeOH. The basicity of the μ₄-Te ligand in the octahedral cluster anion [(μ₄-Te)₂Mn₄(CO)₁₂]²⁻ is demonstrated by its binding to the fragment [(TeMe₂)Mn(CO)₄]⁺ in an axial fashion to afford the novel cluster 1 .     

Synthesis and Structural Characterization of [Cu20Se4(μ3‐SePh)12(PPh3)6] and [Ag(SePh)]∞

Reaction of lithium phenylselenothiolate, generated in situ from the reductive cleavage of PhSe‐SiMe₃ with alkyl lithium reagents and insertion of elemental sulfur, with triphenylphosphine solubilized CuCl affords the molecular cluster complex [Cu₂₀Se₄ (μ₃‐SePh)₁₂(PPh₃)₆] ( 1 ). The analogous reaction with AgCl yields the extended structure [Ag(SePh)]_∞ ( 2 ) in which an infinite layer of Ag^I atoms is capped on either side by μ₄‐SePh ligands. 1: space group P¯1, a = 17.9510(6), b = 18.1712(7), c = 31.4311(11) Å, a = 78.098(2), β = 82.905(2), γ = 70.012(2)°. 2: space group C2/c, a = 5.8762(6), b = 7.2989(7), c = 29.124(2) Å, β = 95.790(3)°.     

Neue Gold‐Selen‐Komplexverbindungen: Synthesen und Strukturen von [Au10Se4(dpppe)4]Br2, [Au2Se(dppbe)]∞, [(Au3Se)2(dppbp)3]Cl2 und [Au34Se14(tpep)6(tpepSe)2]Cl6

Novel Gold Selenium Complexes: Syntheses and Structures of [Au₁₀Se₄(dpppe)₄]Br₂, [Au₂Se(dppbe)]_∞, [(Au₃Se)₂(dppbp)₃]Cl₂, and [Au₃₄Se₁₄(tpep)₆(tpep^Se)₂]Cl₆ The reaction of gold phosphine complexes [(AuX)(PR₃)] (X= halogen; R = org. group) with Se(SiMe₃)₂ yield to new chalcogeno bridged gold complexes. Especially within the use of polydentate phosphine ligands cluster complexes like [Au₁₀Se₄(dpppe)₄]Br₂ ( 1 ) (dpppe = 1, 5‐Bis(diphenylphosphino)pentane), [Au₂Se(dppbe)]_∞ ( 2 ) (1, 4‐Bis(diphenylphosphino)benzene), [(Au₃Se)₂(dppbp)₃]Cl₂ ( 3 ) (dppbp = 4, 4′‐Bis‐diphenylphosphino)biphenyl) und [Au₃₄Se₁₄(tpep)₆(tpep^Se)₂]Cl₆ ( 4 ) (tpep = 1, 1, 1‐Tris(diphenylphosphinoethyl)phosphine, tpep^Se = 1, 1‐Bis(diphenylphosphinoethyl)‐1‐(diphenylselenophosphinoethylphosphine) could be isolated and their structures could be determined by X‐ray diffraction. ( 1: Space group P1 (No. 2), Z = 2, a = 1642.1(11), b = 1713.0(9), c = 2554.0(16) pm, α = 80.41(3)°, β = 76.80(4)°, γ = 80.92(4)°; 2: Space group P2₁/n (No. 14), Z = 4, a = 947.3(2), b = 1494.9(3), c = 2179.6(7) pm, β = 99.99(3)°; 3: Space group P2₁/c (No. 14), Z = 8, a = 2939.9(6), b = 3068.4(6), c = 3114.5(6) pm, β = 109.64(3)°; 4: Space group P1 (No. 2), Z = 1, a = 2013.7(4), b = 2420.6(5), c = 2462.5(5) pm, α = 77.20(3), β = 74.92(3), γ = 87.80(3)°).     

Komplexe mit Antimon‐Liganden: [tBu2(Cl)SbW(CO)5], [tBu2(OH)SbW(CO)5], O[SbPh2W(CO)5]2, E[SbMe2W(CO)5]2 (E = Se,Te), cis‐[(Me2SbSeSbMe2)2Cr(CO)4]

Complexes Containing Antimony Ligands: [^tBu₂(Cl)SbW(CO)₅], [^tBu₂(OH)SbW(CO)₅], O[SbPh₂W(CO)₅]₂, E[SbMe₂W(CO)₅]₂ (E = Se, Te), cis‐[(Me₂SbSeSbMe₂)₂Cr(CO)₄] Syntheses of [^tBu₂(Cl)SbW(CO)₅] ( 1 ), [^tBu₂(OH)SbW(CO)₅] ( 2 ), O[SbPh₂W(CO)₅]₂ ( 3 ), Se[SbMe₂W(CO)₅]₂ ( 4 ), cis‐[(Me₂SbSeSbMe₂)₂Cr(CO)₄] ( 5 ) Te[SbMe₂W(CO)₅]₂ ( 6 ) and crystal structures of 1 – 5 are reported.     

Synthesen und Strukturen der polymeren Silber‐Komplexe [Ag2Cl2(dppbp)3]∞, [Ag2(SPh)2(dppe)3]∞ und [Ag2(SPh)2(triphos)]∞ sowie der Silber‐Chalkogenido‐Cluster [Ag7(SPh)7(dppm)3], {[Ag7(TePh)7(dppp)3]2(dppp)} und [Ag22Cl(SPh)10(PhCOO)11(dmf)3]∞

Syntheses and Structures of the Polymeric Silver Complexes [Ag₂Cl₂(dppbp)₃]_∞, [Ag₂(SPh)₂(dppe)₃]_∞ and [Ag₂(SPh)₂(triphos)]_∞ as well as the Silver Chalcogenido Clusters [Ag₇(SPh)₇(dppm)₃], {[Ag₇(TePh)₇(dppp)₃]₂(dppp)}, and [Ag₂₂Cl(SPh)₁₀(PhCOO)₁₁(dmf)₃]_∞ The reaction of silver carboxylate with silylated chalcogen compounds have been found to have a possibility for the synthesis of metal‐chalcogenide‐custers. Especially phosphine ligands have been found to be useful in stabilising the cluster cores. Some of the silver carboxylate phosphine complexes, which are formed in‐situ, ([Ag₂Cl₂(dppbp)₃]_∞ ( 1 )) and some silver chalcogen complexes ([Ag₂(SPh)₂(dppe)₃]_∞ ( 2 ) und [Ag₂(SPh)₂(triphos)]_∞ ( 3 )), could be isolated and characterised by X‐ray diffraction. Using special reaction conditions, it is possible to isolate cluster species like [Ag₇(SPh)₇(dppm)₃] ( 4 ), {[Ag₇(TePh)₇(dppp)₃]₂(dppp)} ( 5 ) and [Ag₂₂Cl(SPh)₁₀(PhCOO)₁₁(dmf)₃]_∞ ( 6 ) beside the complex compounds. 1: Space group P2₁/n (No. 14), Z = 2, a = 1336, 1(2), b = 2081, 2(5), c = 2015, 4(4) pm, β = 99, 87(2)°; 2: Space group P2₁/n (No. 14), Z = 2, a = 1416, 1(3), b = 1874, 7(4), c = 1444, 8(3) pm, β = 93, 26(3)°; 3: Space group P2₁/n (No. 14), Z = 4, a = 1456, 8(3, b = 1890, 2(4), c = 1916, 1(4) pm, β = 99, 11(3)°; 4: Space group P2₁/n (No. 14), Z = 4, a = 1570, 2(3), b = 2798, 5(6), c = 2752, 7(6) pm, β = 98, 02(3)°; 5: Space group P1 (No. 2), Z = 2, a = 2115, 5(4), b = 2553, 3(5), c = 3188, 7(6) pm, α = 68, 87(3)°, β = 74, 05(3)°, γ = 69, 70(3)°; 6: Space group P1 (No. 2), Z = 2, a = 1583, 0(3), b = 1709, 6(3), c = 2990, 0(6) pm, α = 80, 41(3)°, β = 88, 86(3)°, γ = 71, 10(3)°).     

[Ga6R8]2– (R = SiPh2Me): Eine metalloide Clusterverbindung mit einem unerwarteten Ga6‐Gerüst

[Ga₆R₈]^2– (R = SiPh₂Me): A Metalloid Cluster Compound with an Unexpected Ga₆‐Frame The reaction of a metastable solution of GaBr with a solution of LiSiPh₂Me in a toluene/THF mixture results in orange coloured crystals of [Ga₆(SiPh₂Me)₈]^2– · 2 [Li(THF)₄]⁺ ( 1 ). The unexpected structure of the planar Ga₆ frame (C_2h) could also be realized with the help of DFT calculation. DFT calculations furthermore show that 1 is energetically favoured against an octahedral Ga₆R₆^2– species and R₂. In contrast calculations for the similar Al and B species show that in these cases the octahedral entities are favoured. These results demonstrate that even for similar compounds of B, Al, and Ga Wade rules are too general and that they cannot predict the correct structure. Moreover the atomic arrangement within 1 shows that a structure is preferred which is also present in allotropic β‐Ga and that therefore clusters of this type should be called metalloid or more general elementoid.     

Formation of an Acyl‐Ethynyl‐Methylidyne Complex of Cobalt: Structure of Co3{μ3‐CC(O)C≡C[Ru(dppe)Cp*]}(CO)8(PPh3)

The reaction between Ru(C≡CH)(dppe)Cp* and Co₃(μ₃‐CBr)(CO)₉ in the presence of Pd(PPh₃)₄/CuI afforded dark red Co₃{μ₃‐CC(O)C≡C[Ru(dppe)Cp*]}(CO)₈(PPh₃), whose formation may involve attack of the Ru‐ethynyl fragment on an intermediate cluster‐bound CCO ligand; abstraction of PPh₃ from the palladium catalyst also occurs.     

Hexatellurium Rings in Coordination Polymers and Molecular Clusters: Synthesis and Crystal Structures of [M(Te6)]X3 (M = Rh,Ir; X = Cl,Br, I) and [Ru2(Te6)](TeBr3)4(TeBr2)2

The reaction of an electron‐rich transition metal M (M = Ru, Rh, Ir), tellurium and TeX₄ (X = Cl, Br, I) resulted in black crystals of five ternary coordination polymers with the general composition [M^III(Te₆)]X₃ (M = Rh, Ir) and of the molecular cluster compound [Ru^II₂(Te₆)](Te^IIBr₃)₄(Te^IIBr₂)₂. X‐ray diffraction on single‐crystals revealed that the compounds [M(Te₆)]X₃ crystallize isostructurally in the trigonal space group type R$\bar{3}$ c. In their crystal structures linear, positively charged [M^III(Te₆)] chains form the motif of a hexagonal rod packing. In the chain, each of the formally uncharged Te₆ molecules with chair conformation acts as a bis‐tridentate bridging ligand to two M atoms. The octahedrally coordinated M atoms are spiro atoms in the chain of trans vertices sharing heterocubane fragments. Including the isolated halide ions, which provide charge balance, the entire arrangement resembles a cut‐out of the α‐polonium structure type.In the monoclinic compound Ru₂Te₁₂Br₁₆ (space group P2₁/n), the ruthenium atoms of the hetero‐cubane core of the molecular cluster [Ru₂(Te₆)](TeBr₃)₄(TeBr₂)₂ are saturated by terminal bromidotellurate(II) groups. Again, the Te₆ ring is formally uncharged. With the tellurium atoms acting as electron‐pair donors the 18 electron rule is fulfilled for the M atoms in all compounds.     

Neue Silber‐Tellurid Cluster stabilisiert mit zweizähnigen Phosphanen: Synthese und Struktur von {[Ag5(TePh)6(Ph2P(CH2)2PPh3)](Ph2P(CH2)2PPh2)}∞, [Ag18Te(TePh)15(Ph2P(CH2)3PPh2)3Cl] und [Ag38Te13(TetBu)12(Ph2P(CH2)2PPh2)3]

Novel Silver‐Telluride Clusters Stabilised with Bidentate Phosphine Ligands: Synthesis and Structure of {[Ag₅(TePh)₆(Ph₂P(CH₂)₂PPh₃)](Ph₂P(CH₂)₂PPh₂)}_∞, [Ag₁₈Te(TePh)₁₅(Ph₂P(CH₂)₃PPh₂)₃Cl], and [Ag₃₈Te₁₃(Te t Bu)₁₂(Ph₂P(CH₂)₂PPh₂)₃] Bidentate phosphine ligands have been found effective to stabilise polynuclear cores containing silver and chalcogenide ligands. They can act as intra and intermolecular bridges between the silver centres. The clusters {[Ag₅(TePh)₆(Ph₂P(CH₂)₂PPh₃)](Ph₂P(CH₂)₂PPh₂)}_∞ ( 1 ), [Ag₁₈Te(TePh)₁₅(Ph₂P(CH₂)₃PPh₂)₃Cl] ( 2 ), and [Ag₃₈Te₁₃(TetBu)₁₂(Ph₂P(CH₂)₂PPh₂)₃] ( 3 ) have been prepared and their molecular structure determined. Compound 2 and 3 are molecular structures with separated cluster cores while 1 forms a polymeric chain bridged by phosphine ligands. ( 1 : space group P2₁/c (No. 14), Z = 4, a = 3518,1(7) pm, b = 2260,6(5) pm, c = 3522,1(7) pm, β = 119,19(3)°; 2 : space group R3 (No. 148), Z = 6, a = b = 3059,4(4) pm, c = 5278,8(9) pm; 3: space group Pccn (No. 56), Z = 4, a = 3613,0(9) pm, b = 3608,6(7) pm, c = 2153,5(8) pm)     

Synthesis and Structure of the Clusters [Hg2(μ—SePh)2(SePh)2(PPh3)2] and [Hg3Br3(μ—SePh)3] · 2 DMSO

The compounds [Hg₂(μ—SePh)₂(SePh)₂(PPh₃)₂] ( I ) and [Hg₃Br₃(μ—SePh)₃] · 2 DMSO ( II ) are formed by reactions of [Hg(SePh)₂] with PPh₃ in THF( I ) or with HgBr₂ in DMSO ( II ) at room temperature. X—ray crystallography reveals that the cluster I consists of a distorted square built by each two Hg and Se atoms. The Hg atoms have almost tetrahedral co‐ordination environments formed by selenium atoms of two (μ‐^—SePh) ligands and Se and P atoms of terminal ^—SePh and PPh₃ ligands. The compound II is a six‐membered ring with alternating Hg and Se atoms in the chair conformation. Two DMSO molecules occupy positions below and above the [Hg₃Se₃] ring with the oxygen atoms directed to the centre of the ring.     

Synthesis and Crystal Structure of the Azide K4[Re6Sei8(N3)a6]·4H2O; Luminescence,Redox, and DFT Investigations of the [Re6Sei8(N3)a6]4– Cluster Unit

The reaction of K₄[Re₆Seⁱ₈(OH)^a₆] · 8H₂O with NaN₃ in water results in the formation of [Re₆Seⁱ₈(N₃)^a]^4– units that crystallize with K⁺ and H₂O to form K₄[Re₆Seⁱ₈(N₃)^a₆] · 4H₂O [P2₁/c (N°14), a = 9.0595(3) Å, b = 13.2457(4) Å, c = 13.2040(5) Å, β = 94.472(1)°]. In the solid state, the unit is characterized by N₃ linear groups forming bond angles of roughly 120° with the Re₆ cluster. The positions of the ν_as and ν_sy bands as well as N–N–N deformation modes of the N₃ groups are discussed. Luminescence properties of the [Re₆Seⁱ₈(N₃)^a]^4– unit were measured in the solid state and in an acetonitrile solution. The redox potential of the [Re₆Seⁱ₈(N₃)^a]^4–/[Re₆Seⁱ₈(N₃)^a]^3– system was measured in acetonitrile. Experimental results were analyzed in the light of density functional theory calculations.     

Preparation,Spectroscopic Properties,and Crystal Structures of Fe2(CO)6(μ‐CO)(μ‐CF2)2, Fe2(CO)6(μ‐CO)2(μ‐CF2), and Fe2(CO)6(μ‐CF2)(PPh3)2 – Theoretical Studies of Methylenic vs. Carbonyl Bridges in Diiron Complexes

The reaction of Na₂[Fe(CO)₄] with Br₂CF₂ in n‐pentane generates a mixture of the compounds (CO)₃Fe(μ‐CO)_3–n(μ‐CF₂)_nFe(CO)₃ ( 2 , n = 2; 3 , n = 1) in low yields with 3 as the main product. 3 is obtained free from 2 by reacting Br₂CF₂ with Na₂[Fe₂(CO)₈]. The non‐isolable monomeric complex (CO)₄Fe=CF₂ ( 1 ) can probably considered as the precursor for 2 . 3 reacts with PPh₃ with replacement of two CO ligands to form Fe₂(CO)₆(μ‐CF₂)(PPh₃)₂ ( 4 ). The complexes 2 – 4 were characterized by single crystal X‐ray diffraction. While the structure of 2 is strictly similar to that of Fe₂(CO)₉, the structure of 3 can better be described as a resulting from superposition of the two enantiomers 3 a and 3 b with two semibridging CO groups. Quantum chemical DFT calculations for the series (CO)₃Fe(μCO)_3–n(μ‐CF₂)_nFe(CO)₃ (n = 0, 1, 2, 3) as well as for the corresponding (μ‐CH₂) derivatives indicate that the progressively larger σ donor and π acceptor properties for the bridging ligands, in the order CO < CF₂ < CH₂, favor a stronger Fe–Fe bond.     

Synthesis,Structure and Isomerism of the [Fe<Subscript>3</Subscript>Pt(μ<Subscript>4</Subscript>-Q)(CO)<Subscript>9</Subscript>(dppm)] Clusters (Q = Se,Te; dppm = Ph<Subscript>2</Subscript>PCH<Subscript>2</Subscript>PPh<Subscript>2</Subscript>)

The reaction of K₂[Fe₃(μ₃-Q)(CO)₉] (Q = Se (K₂[1a]), Te (K₂[1b])) with [(dppm)PtCl₂] leads to the addition of a [(dppm)Pt]²⁺ unit to a Fe₂Q face of the initial cluster. By this way new heteronuclear clusters [Fe₃Pt(μ₃-Q)(CO)₉(dppm)] were obtained possessing a butterfly-shaped cluster core bridged by a μ₄-Q unit. It has been found that the resulting Fe-Pt clusters exist as equilibrium mixtures of two isomeric forms in solution differing by the dppm coordination mode: as a chelate ligand coordinated to Pt or as a bridging ligand coordinated to Pt and Fe atoms. The mixtures of isomers can be separated by chromatography and the pure isomers can be isolated as stable crystalline phases. Solutions of both isomers attain equilibrium at normal conditions in about 1 month as found by NMR. Dedicated to Professor Dieter Fenske in the occasion of his 65th birthday.     

Theoretical Comparison of the Bonding in CpCr(CO)2(NX) [X = O,S, Se,Te]

Molecular orbital calculations employing the PM3 model have been used to examine the bonding in the complexes CpCr(CO)₂(NX) (X = O, S, Se, Te). The previously established trend of increasing Cr-N interaction as X changes from O to S is demonstrated by these calculations, and found to extend to Se and Te. Bond lengths, bond orders, vibrational frequencies, and heats of reaction are used to support the conclusion that metal to ligand π-backbonding increases down the periodic chart from NO to NTe.