Syntheses of trimethoxysilyl‐endcapped polylactones via 3‐mercaptopropyl trimethoxysilane

Monofunctional polylactones were prepared by Bu₂Sn(OMe)₂‐initiated ring‐opening polymerization of ε‐caprolactone (εCL) followed by acylation with bromoacetylbromide. Telechelic polylactones and polylactides were prepared via ring‐expansion polymerization with 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane (DSDOP) or 2,2‐dibutyl‐2‐stanna‐pentaoxacyclotridecane (Bu₂SnTEG) as cyclic initiator. In situ combination of the polymerization with condensation by means of bromoacetylbromide yielded polylactones having bromoacetate endgroups. These endgroups were subjected to nucleophilic substitution with 3‐mercaptopropyl trimethoxysilane (3‐MPTMS). Analogous experiments were conducted with dl‐lactide. The telechelic trimethoxysilyl‐endcapped polylactones were characterized by viscosity, ¹H and ¹³C NMR‐spectroscopy, and MALDI‐TOF mass spectrometry. The mass spectra revealed small amounts of cyclic oligolactones as byproducts in all samples. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3667–3674, 2005     

Molybdenum‐ and Tungsten‐Based Coordination Polymers as Catalysts for an Efficient and Rapid Synthesis of Hexahydro‐5‐oxoquinoline‐3‐carboxylates and 1,4‐Dihydropyridine‐3,5‐dicarboxylates

Hexahydro‐5‐oxoquinoline‐3‐carboxylates and 1,4‐dihydropyridine‐3,5‐dicarboxylates were synthesized efficiently and rapidly (2 min) in the presence of molybdenum‐ and tungsten‐based coordination polymers [M(Bu₃Sn)₂O₄)]_n (M=Mo or W) as catalysts (Schemes 1 and 2; Tables 2 and 3). The products were formed at room temperature in excellent yields (90–98%). The catalysts worked under heterogeneous conditions and were recyclable. The earlier reports for the application of these polymers to conduct organic synthesis are limited. The present method explores a new and useful application of these catalysts.     

The grafting of acrylamide onto poly(ε‐caprolactone) and poly(1,5‐dioxepan‐2‐one) using electron beam preirradiation. II. An in vitro degradation study on grafted poly(ε‐caprolactone)

Acrylamide was graft polymerized onto the surface of a biodegradable semicrystalline polyester, poly(ε‐caprolactone). Electron beam irradiation at a dose of 5 Mrad was used to generate initiating species in the polyester. The degradation in vitro at pH 7.4 and 37°C in a phosphate buffer solution was studied for untreated, irradiated and acrylamide‐grafted polymers. In the case of poly(ε‐caprolactone), all materials showed similar behavior in terms of weight loss. No significant decrease in weight was observed up to 40 weeks, after which the loss of weight accelerated. The main differences in degradation behavior were found for the average molecular weights, M̄_n and M̄_w. Virgin poly(ε‐caprolactone) maintained M̄_n and M̄_w up to about 40 weeks, whereas the irradiated and grafted poly(ε‐caprolactone) showed similar continuous declines in M̄_n and M̄_w throughout the degradation period. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1651–1657, 1999     

New Polymer Syntheses, 108. Controlled Degradation and In‐Situ Functionalization of Polycarbonates by Means of Bu2SnO

It was found that diphenyl carbonate reacts with Bu₂SnO above 140°C yielding CO₂ and Bu₂Sn(OPh)₂. This insertion reaction was also successfully applied to a polycarbonate prepared from polytetrahydrofuran diol‐1000 and Bu₂SnO containing macrocyclic polyTHF dioxides. Bu₂SnO reacted analogously with poly(bisphenol A) carbonates yielding tin‐containing rapidly crystallizing cyclic oligocarbonates. Their treatment with 1,2‐ethanedithiol gave linear oligocarbonates having two OH end groups. Bu₂Sn‐containing macrocyclic oligocarbonates reacted in‐situ with several carboxylic acid chlorides, forming telechelic oligocarbonates with functional ester end groups. Bu₂Sn‐containing macrocycles also reacted in‐situ with terephthaloyl chlorides yielding a poly(ester carbonate).     

Synthesis,spectroscopic characterization,and biological activity studies of organotin(IV) derivatives of (E)‐3‐(3‐fluorophenyl)‐2‐phenyl‐2‐propenoic acid. Crystal and molecular structure of Et2Sn[OCOC(C6H5)CH(3‐FC6H4)]

The complexes Me₂SnL₂ ( I ), Me₃SnL ( II ), Et₂SnL₂ ( III ), n‐Bu₂SnL₂ ( IV ), n‐Bu₃SnL ( V ), n‐Oct₂SnL₂ ( VI ), Bz₂SnL₂ ( VII ), and Ph₃SnL ( VIII ), where “L” is ( E )‐3‐(3‐fluorophenyl)‐2‐phenyl‐2‐propenoate, have been prepared and structurally characterized by means of elemental analysis, infrared, mass, and multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR spectral techniques. The spectroscopic results showed that the geometry around the Sn atom in triorganotin(IV) derivatives is four‐coordinated in noncoordinating solvent and behaves as five‐coordinated linear polymers with bridging carboxylate groups or five‐coordinated monomers, both acquiring trans‐R₃SnO₂ geometry for Sn in the solid state. While all the diorganotin(IV) derivatives may acquire trigonal bipyramidal structures in solution due to collapse of the Sn←OCO interaction and octahedral geometries in the solid state, which have been confirmed by the X‐ray crystallographic data of the compound III . The crystal structure of Et₂SnL₂ ( III ) has been determined by X‐ray crystallography and is found skew‐trapezoidal bipyramidal, which substantiates that the ligand acts as an anisobidentate chelating agent, thus rendering the Sn atom six coordinated. The crystal is monoclinic with space group C2₁/n. All the investigated compounds have also been screened for biocidal and cytotoxicity data. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:420–432, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20243     

Synthesis of Styrenic‐Terminated Methacrylate Macromonomers by Nitroanion‐Initiated Living Anionic Polymerization

N‐Isopropyl‐4‐vinylbenzylamine (PVBA) was synthesized and used as an initiator for the polymerization of methacrylates to synthesize macromonomers with terminal styrenic moieties. LiPVBA initiated a living polymerization and block copolymerization of methyl methacrylate, 2‐(N,N‐dimethylamino)ethyl methacrylate and tert‐butyl methacrylate and produced polymers having well‐controlled molecular weights and very low polydispersities (M̄_w/M̄_n < 1.1) in quantitative yield. ¹H NMR analysis revealed that the polymers contained terminal 4‐vinylbenzyl groups. The macromonomers were reactive in the copolymerization with styrene.     

Controlled polymerization of ϵ-caprolactone -from macromolecules to microspheres

Pseudoanionic polymerization of ϵ-caprolactone (CL), initiated with dialkylaluminum alkoxides, was used for the tailored synthesis of poly(CL) with M̄_n ≤ 100 000 and M̄_w /M̄_n < 1. 20. Macromolecules with functional groups at one or at both ends were obtained in this way. Controlled polymerization of CL allowed to prepare poly(dodecyl acrylate)-g-poly(ϵ-caprolactone) (poly(DAC)-g-poly(CL)) with well defined poly(CL) grafts. These copolymers were used as the surface active agents for the direct synthesis of poly(CL) microspheres. The number average diameter (D̄_n ) of poly(CL) microspheres varied from 0.628 μm to 0.94 μm and the diameter polydispersity (D̄_v /D̄_n ) varied from 1.038 to 1.26, depending on the composition of poly(DAC)-g-poly(CL). Human serum albumin (HSA) and human gamma globulins (_γ G) were attached to the poly(CL) microspheres. The maximal surface concentrations of HSA and _γ G adsorbed onto the microspheres were equal to 9·10⁻⁴ g/m² and 2.0·10⁻³ g/m² respectively.     

Transesterification of oligomeric dialkyl phosphonates,leading to the high‐molecular‐weight poly‐H‐phosphonates

Polycondensation of 1,10‐decanediol with dimethyl‐H‐phosphonate taken in excess leads to oligomers with methyl‐H‐phosphonate end groups. The polytransesterification of the resulting oligomer as well as the related model reactions were studied. The synthesis of poly(decamethylene‐H‐phosphonate) was analyzed and the final product had M̄_n = 1.4–1.9 10⁴ (from end groups, vpo, and M̄_n of the derived polymers). The exchange of the ester groups between two homoesters (dimethyl and diethyl phosphonates) used as models, conducted at r.t. and catalyzed by metal alkoxide provides mixed (hetero) ester in a few minutes. If the concentration of the catalyst is not high enough, then the reaction does not go to equilibrium, because the alcoholate anions are converted into the anions of monoesters of the H‐phosphonic acid, catalytically inactive at this temperature. However, these monoesters become catalytically active at higher temperature, i.e., at the conditions used for preparing higher molecular‐weight products by transesterification. The apparent rate constants (k̄) of the ester exchange catalyzed by monoester salt (modeling the propagation step in polytransesterification) were determined by two independent methods; at 130°C k̄ ∼ 1.0 · 10⁻² mol⁻¹ · L · s⁻¹. The detailed study of the model polytransesterification, and particularly of the polymer end groups appearance and disappearance (studied by ¹H‐, ¹³C‐, and ³¹P‐NMR) allowed postulation of the reaction mechanism and confirmed our previous work, describing formation at these conditions of polymers with M̄_n > 10⁴. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1365–1381, 1999     

Synthesis and Molecular Structure of [n‐Bu2(F)SnOSn(F)t‐Bu2]2 — an Unsymmetrically Substituted Tetraorganodistannoxane

The dimeric tetraorganodistannoxane [n‐Bu₂(F)SnOSn(F)t‐Bu₂]₂ ( 1 ) was prepared by the reaction of (t‐Bu₂SnO)₃ with n‐Bu₂SnF₂ and characterized in solution by multinuclear NMR spectroscopy and ESI MS spectrometry and in the solid state by ¹¹⁹Sn MAS NMR spectroscopy and single crystal X‐ray diffraction.     

Transmetallierung von Zinn(II) in [Sn(μ3‐PSitBu3)]4 durch Barium – von Sn4P4‐Heterocuban‐Strukturen zu heterobinuklearen Käfigverbindungen mit einem zentralen BanSn4−nP4‐Heterocuban‐Polyeder (n = 1, 2 und 3)

Transmetallation of Tin(II) in [Sn(μ₃‐PSitBu₃)]₄ by Barium – from Sn₄P₄ Heterocubane Structures to Heterobinuclear Cage Compounds with a Central Ba_nSn_4?nP₄ Heterocubane Polyhedron (n = 1, 2 and 3) For the preparation of compounds of the type [Ba_nSn_4?n(PSitBu₃)₄] (n = 1 ( 2 ), 2 ( 3 ) and 3 ( 4 )) two synthetic routes are applicable: in the transmetallation reaction homometallic [Sn₄(PSitBu₃)₄] ( 1 ) reacts with barium metal and in a deprotonation reaction (metallation) tri(tert‐butyl)silylphosphane reacts simultaneously with (thf)₂Ba[N(SiMe₃)₂]₂ and Sn[N(SiMe₃)₂]₂. During the transmetallation reaction mixtures of the heterobimetallic cage compounds 2 to 4 are obtained, however, analytically pure compounds 2 and 3 are accessible by the metallation reaction. Compound 4 is formed as a minor product together with 3 . Due to the larger Ba‐P bond lengths compared to the Sn‐P values the substitution of tin by barium leads to strong distortions of the heterocubane moiety. With NMR‐spectroscopic experiments one could show that all the above mentioned compounds form Ba_nSn_4?nP₄ heterocubane cage structures.     

Self‐Assembly of Dialkyltin Moieties and Mercaptobenzoic Acid into Macrocyclic Complexes with Hydrophobic “Pseudo‐Cage” or Double‐Cavity Structures: Supramolecular Infrastructures Involving Intermolecular C?H⋅⋅⋅S Weak Hydrogen Bonds and π–π Interactions

Four novel organotin complexes of two types—[R₂Sn(o‐SC₆H₄CO₂)]₆ (R=Me, 1 ?H₂O; nBu, 2 ) and {[R₂Sn(m‐CO₂C₆H₄S)R₂Sn(m‐SC₆H₄CO₂)SnR₂]O}₂ (R=Me, 3 ; nBu, 4 )—have been prepared by treatment of o‐ or m‐mercaptobenzoic acid and the corresponding R₂SnCl₂ (R=Me, nBu) with sodium ethoxide in ethanol (95 %). All the complexes were characterized by elemental analysis, FT‐IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy, TGA, and X‐ray crystallography diffraction analysis. The molecular structure analyses reveal that both 1 and 2 are hexanuclear macrocycles with hydrophobic “pseudo‐cage” structures, while 3 and 4 are hexanuclear macrocycles with double‐cavity structures. Furthermore, the supramolecular structure analyses show that looser and more intriguing supramolecular infrastructures were also found in complexes 1 – 4 , which exist either as one‐dimensional chains of rings or as two‐dimensional networks assembled from the organometallic subunits through intermolecular C? H???S weak hydrogen bonds (WHBs) and π–π interactions.     

Sandwich Double‐Decker Lanthanide(III) “Intracavity” Complexes Based on Clamshell‐Type Phthalocyanine Ligands: Synthesis,Spectral, Electrochemical,and Spectroelectrochemical Investigations

Phthalocyanine compounds of novel type based on a bridged bis‐ligand, denoted “intracavity” complexes, have been prepared. Complexation of clamshell ligand 1,1′‐[benzene‐1,2‐diylbis(methanediyloxy)]bis[9(10),16(17),23(24)‐tri‐tert‐butylphthalocyanine] (^clam,tBuPc₂H₄, 1 ) with lanthanide(III) salts [Ln(acac)₃] ? n H₂O (Ln=Eu, Dy, Lu; acetylacetonate) led to formation of double‐deckers ^clam,tBuPc₂Ln ( 2 a – c ). Formation of high molecular weight oligophthalocyanine complexes was demonstrated as well. The presence of an intramolecular covalent bridge affecting the relative arrangement of macrocycles was shown to result in specific physicochemical properties. A combination of UV/Vis/NIR and NMR spectroscopy, MALDI‐TOF mass‐spectrometry, cyclic voltammetry, and spectroelectrochemistry provided unambiguous characterization of the freshly prepared bis‐phthalocyanines, and also revealed intrinsic peculiarities in the structure–property relationship, which were supported by theoretical calculations. Unexpected NMR activity of the paramagnetic dysprosium complex 2 b in the neutral π‐radical form was observed and examined as well.     

Organotin(IV) esters of (E)‐3‐furanyl‐2‐phenyl‐2‐propenoic acid: Synthesis,investigation of the coordination modes by IR,multinuclear NMR (1H, 13C, 119Sn) and In Vitro biological studies

Complexes [Me₂SnL₂ ( I ), Me₃SnL ( II ), Et₂SnL₂ ( III ), n‐Bu₂SnL₂ ( IV ), n‐Bu₃SnL ( V ), n‐Oct₂SnL₂ ( VI )], where L is (E)‐3‐furanyl‐2‐phenyl‐2‐propenoate, have been synthesized and structurally characterized by vibrational and NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopic techniques in combination with mass spectrometric and elemental analyses. The IR data indicate that in both the di‐ and triorganotin(IV) carboxylates the ligand moiety COO acts as a bidentate group in the solid state. The ¹¹⁹Sn NMR spectroscopic data, ¹J[¹¹⁹Sn,¹³C] and ²J[¹¹⁹Sn, ¹H], coupling constants show a four‐coordinated environment around the tin atom in triorganotin(IV) and five‐coordinated in diorganotin(IV) carboxylates in noncoordinating solvents. The complexes have been screened against bacteria, fungi, and brine‐shrimp larvae to assess their biological activity. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:612–620, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20488     

Bismuth halide‐catalyzed polymerizations of ε‐caprolactone

In contrast to BiF₃, the other three Bi‐halides catalyzed the ring‐opening polymerization of ε‐caprolactone (ε‐CL) in bulk. A temperature of 140 °C was found to be advantageous for rapid polymerization and optimum molecular weights. At this temperature, the reactivity of the catalysts increases in the order BiCl₃ < BiBr₃ < BiJ₃. Variation of the monomer‐catalyst ratio (M/C) yielded number‐average molecular weights (M_ns) up to 80,000 Da (corrected SEC data, 120,000 Da uncorrected), but a proper control of the M_ns was not achieved. In addition to CH₂? OH endgroups, CH₂Cl, CH₂Br, and CH₂J endgroups were detected, but no evidence for a cationic polymerization mechanism was found. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7483–7490, 2008     

Hexakis(2,4,6‐triisopropylphenyl)cyclotristannoxane – a Molecular Diorganotin Oxide with Kinetically Inert Sn–O Bonds

The single‐crystal X‐ray structure analysis of hexakis(2,4,6‐triisopropylphenyl)cyclotristannoxane, cyclo‐[(2,4,6‐i‐Pr₃‐C₆H₂)₂SnO]₃ ( 1 ), is reported and reveals this compound to contain an almost planar six‐membered ring. Redistribution reactions of 1 with cyclo‐(t‐Bu₂SnO)₃ and t‐Bu₂SiCl₂, respectively, failed and indicate an unusual kinetic inertness of the Sn–O bonds in 1 as compared to related molecular diorganotin oxides containing less bulkier substituents. The redistribution reaction of cyclo‐(t‐Bu₂SnO)₃ with cyclo‐(t‐Bu₂SnS)₂ leads to an equilibrium involving the trimeric diorganotin oxysulphides cyclo‐t‐Bu₂Sn(OSnt‐Bu₂)₂S ( 2 a ) and cyclo‐t‐Bu₂Sn(SSnt‐Bu₂)₂O ( 2 b ).     

Synthesis, Characterization and Biological Activity of Diorganotin（IV） Complexes of N-（3,5-Dibromosalicylidene）-α-amino Acid

The diorganotin（Ⅳ） complexes of N-（3,5-dibromosalicylidene）-α-amino acid, R2Sn（2-O-3,5-Br2C6H2CH= NCHRCOO）（where R=H, Me, i-Pr, Bz; R＇=n-Bu, Cy）, were synthesized by the reactions of diorganotin dichlorides with in situ formed potassium salt of N-（3,5-dibromosalicylidene）-α-amino acid and characterized by elemental analysis, IR and NMR （^1H, ^13C and ^119Sn） spectra. The crystal structures of n-Bu2Sn（2-O-3,5-Br2C6H2CH= NCHRCOO）（R=i-Pr, Bz） and Cy2Sn（2-O-3,5-Br2C6H2CH=NCHRCOO）（R=Me, Bz） were determined by X-ray single crystal diffraction and showed that the tin atoms are in a distorted trigonal bipyramidal geometry to form five- and six-membered chelate rings with the tridentate ligand. Bioassay results indicated that the compounds possess better in vitro antitumour activity against three human tumour cell lines, HeLa, CoLo205 and MCF-7, than cis-platin and moderate anti-bacterial activity against two bacteria, E. coli and S. aureus.     

Synthesis,structural characterization and cytotoxic activity of diorganotin(IV) complexes of N‐(5‐halosalicylidene)‐α‐amino acid

Fourteen new diorganotin(IV) complexes of N‐(5‐halosalicylidene)‐α‐amino acid, R′₂Sn(5‐X‐2‐OC₆H₃CH?NCHRCOO) (where X = Cl, Br; R = H, Me, i‐Pr; R′ = n‐Bu, Ph, Cy), were synthesized by the reactions of diorganotin halides with potassium salt of N‐(5‐halosalicylidene)‐α‐amino acid and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ¹¹⁹Sn) spectra. The crystal structures of Bu₂Sn(5‐Cl‐2‐OC₆H₃CH?NCH(i‐Pr)COO) and Ph₂Sn(5‐Br‐2‐OC₆H₃CH?NCH(i‐Pr)COO) were determined by X‐ray single‐crystal diffraction and showed that the tin atoms are in a distorted trigonal bipyramidal geometry and form five‐ and six‐membered chelate rings with the tridentate ligand. Bioassay results of a few compounds indicated that the compounds have strong cytotoxic activity against three human tumour cell lines, i.e. HeLa, CoLo205 and MCF‐7, and the activity decreased in the order Cy>n‐Bu>Ph for the R′ group bound to tin. Copyright © 2005 John Wiley & Sons, Ltd.     

Cationic organotin cluster [t‐Bu2Sn(OH)(H2O)]22+2OTf−‐catalyzed one‐pot three‐component syntheses of 5‐substituted 1H‐tetrazoles and 2,4,6‐triarylpyridines in water

The cationic organotin cluster [t‐Bu₂Sn(OH)(H₂O)]₂²⁺2OTf^? is easy to prepare and stable in air. The catalytic activity of [t‐Bu₂Sn(OH)(H₂O)]₂²⁺2OTf^? as a neutral organotin Lewis acid catalyst is probed through the one‐pot three‐component syntheses of 5‐substituted 1H‐tetrazoles from aldehydes, hydroxylamine hydrochloride and sodium azide, and of 2,4,6‐triarylpyridines from aromatic aldehydes, substituted acetophenones and ammonium acetate. The reactions proceed well in the presence of 1 mol% of [t‐Bu₂Sn(OH)(H₂O)]₂²⁺2OTf^? in water and provide the corresponding 5‐substituted 1H‐tetrazoles and 2,4,6‐triarylpyridines in good to excellent yields. The method reported has several advantages such as the catalyst being neutral, low catalyst loading and use of water as a green solvent.     

Lithiated Stannasilanes – Building Blocks for Monocyclic Si–Sn Rings

Dilithiated di(stannyl)oligosilanes (^tBu₂Sn(Li)– (SiMe₂)_n–Sn(Li)^tBu₂; 4 , n = 2; 5 , n = 3) were synthesized by the reaction of lithium diisopropylamide (LDA) with the α,ω‐hydrido tin substituted oligosilanes (^tBu₂Sn(H)– (SiMe₂)_n–Sn(H)^tBu₂; 1 , n = 2; 2 , n = 3). Surprisingly, the reaction of 1 and 3 (^tBu₂Sn(H)–(SiMe₂)₄–Sn(H)^tBu₂) with LDA resulted not in the formation of the lithiated compound, but what one can find is the formation of the 5,5‐ditert.butyl‐octamethyl‐1,2,3,4‐tetrasila‐5‐stannacyclopentane ( 8 ) (n = 4) in addition to the expected product 4 (n = 4) and the 3,3,6,6‐tetratert.butyl‐octamethyl‐1,2,4,5‐tetrasila‐3,6‐distannacyclohexane ( 7 ) (n = 3). Reactions of 4 and 5 with dimethyl and diphenyldichlorosilanes yielding monocyclic Si–Sn derivatives ( 9 – 11 ) are also discussed. The solid‐state structures of 7 and 11 were determined by X‐ray crystallography.     

Heteroleptic [n]Chromoarenophanes: ansa Complexes Derived from [Cr(η5‐C5H5)(η6‐C6H6)]

The synthesis of ansa complexes has been studied intensively owing to their importance as homogeneous catalysts and as precursors of metal‐containing polymers. However, paramagnetic non‐metallocene derivatives are rare and have been limited to examples with vanadium and titanium. Herein, we report an efficient procedure for the selective dilithiation of paramagnetic sandwich complex [Cr(η⁵‐C₅H₅)(η⁶‐C₆H₆)], which allows the preparation of a series of [n]chromoarenophanes (n=1, 2, 3) that feature silicon, germanium, and tin atoms at the bridging positions. The electronic and structural properties of these complexes were probed by X‐ray diffraction analysis, cyclic voltammetry, and by UV/Vis and EPR spectroscopy. The spectroscopic parameters for the strained and less strained complexes (i.e., with multiple‐atom linkers) indicate that the unpaired electron resides primarily in a d orbital on chromium(I); this result was also supported by density functional theory (DFT) calculations. We did not observe a correlation between the experimental UV/Vis and EPR data and the degree of molecular distortion in these ansa complexes. The treatment of tin‐bridged complex [Cr(η⁵‐C₅H₄)(η⁶‐C₆H₅)SntBu₂] with [Pt(PEt₃)₃] results in the non‐regioselective insertion of the low‐valent Pt⁰ fragment into the C_ipso? Sn bonds in both the five‐ and six‐membered rings, thereby furnishing a bimetallic complex. This observed reactivity suggests that ansa complexes of this type are promising starting materials for the synthesis of bimetallic complexes in general and also underline their potential to undergo ring‐opening processes to yield new metal‐containing polymers.