Volume 64, Issue 1

By cothermolysis of [Cp R Fe(CO) 2 ] 2 [CpR = η 5 -C 5 (CH 2 Ph) 5 (Cp bn ) (1) and η 5 -C 5 Me 4 C 2 H 4 SMe (Cp S ) (2)] with P 4 phosphorus two novel pentaphosphaferrocenes of the formula [Cp R Fe(η 5 -P 5 )] [Cp R = Cp S (3), Cp bn (4)] have been synthesised and comprehensively characterised. These two products represent the first derivatives of this class of compounds with a functionalised as well as a sterically bulky adjacent cyclopentadienyl ligand. The pentabenzylcyclopentadienyl derivative 4 as well as both of the starting materials [Cp R Fe(CO) 2 ] 2 1 and 2 have been additionally characterised by X-ray diffraction structure determinations. The pentaphosphaferrocene 4 represents in the crystal lattice highly aggregated units via intra- and intermolecular π-stacking interactions of the phenyl rings of the Cp bn ligand. Graphical Abstract Neue Pentaphosphaferrocene

Dimeric tri( tert -butyl)cyclopentadienyliron(II) bromide [Cp m Fe(μ-Br)]2 (1) reacts with phenylmagnesium bromide to give the dinuclear di(cyclohexadienylidene) complex [(Cp m Fe)2(μ,η 5 :η 5 -H 5 C 6 =C 6 H 5 )] (2), and with mesitylmagnesium bromide either to the dinuclear complex [Cp m Fe-(μ,η 5 :η 1 -C 6 H 2 Me 3 )Fe(Br)Cp m ] (3) or to the mononuclear mesityl complex [Cp m FeC 6 H 2 Me 3 ] (4), depending on the reaction conditions. The mesityl complex 4 undergoes rearrangement and adds via the mesityl ipso carbon atom to bromide 1 with formation of 3. A similar reaction occurs with the nickel analog of bromide 1. In the latter case, however, mesityl is replaced by tolyl during reaction in toluene, with phenyl in benzene, and remains unchanged if the reaction is carried out in pentane solution. An electrophilic attack at the arene solvent used is discussed for the exchange reaction. For the crystallographically characterized complexes 3 and [CpFe m (μ,η 1 :η 5 -C 6 H 4 Me)Ni(Br)Cp m ] (5) with a meta -tolyl ligand a significant deviation of the Cp m Fe fragment from a symmetrical position above the six-membered ring ligand raises questions regarding a possible contribution of a cyclohexadienylylidene resonance structure. Graphical Abstract High-spin Cyclopentadienyl Complexes, Part 6. σ/π-Rearrangement of Aryl Ligands Connected to Cyclopentadienyliron Fragments

The electron distribution within a mesityl ligand bridging a cyclopentadienyliron fragment attached to the mesityl π system and a second metal fragment connected to the ipso carbon of the mesityl ring has been probed using a copper(I) halide as a component in [Cp m Fe (μ,η 5 :η 1 -C 6 H 2 Me 3 )CuCl] (2) and its copper bromide derivative 3. This approach minimizes steric effects and allows for DFT calculations the results of which are in very good agreement with structural data. The calculations show a significant carbene character already for the bare phenyl anion as a result of electrostatic repulsion of the lone pair pushing the π electrons away from the ipso carbon towards the para carbon atom of the aromatic ring. π Coordination of a cyclopentadienyliron(II) fragment to the phenyl anion to form a hypothetical sandwich complex does not change this situation. The iron center rather follows the unsymmetric distribution of π charge with an unsymmetrical coordination to the π system. Coordination of a copper(I) chloride moiety to the phenyl anion or to the hypothetical π complex [CpFe(C 6 H 5 )] in both cases equally lowers that carbene character by attracting the lone pair of the ipso carbon and thus decreasing its repulsive influence on the π electrons. Graphical Abstract High-spin Cyclopentadienyl Complexes, Part 7. Ambivalent Interpretation of the Bonding in Iron-Copper Complexes: Metalated Arene versus Carbocyclic Carbene

The development of optically active cyclopentadienyl complexes as enantioselective catalysts calls for simple synthetic procedures for cyclopentadienes with optically active alkyl substituents. While exo-bornyl chloride and exo-fenchyl bromide do not react or exclusively eliminate hydrogen halide with cyclopentadienylmetal compounds in ether solvents or ammonia, they undergo Wagner- Meerwein rearrangement and substitution with cyclopentadienylmagnesium chloride in toluene. The bornyl cation yields racemic exo-bornylcyclopentadiene and partially racemized isocamphylcyclopentadiene, but for the fenchyl cation no racemization pathway is available, and the main diastereomer among the lithium salts of the ensuing substituted cyclopentadienes can be isolated in 95% diastereomeric purity by solvent extraction. This material with the IUPAC name lithium (2R)- 2,5,5-trimethylbicyclo[2.2.1]hept-2-ylcyclopentadienide carries an alkyl substituent having no trivial name so far. Exo-norbornylcyclopentadiene could be synthesized in high yield with a similar procedure. The same protocol works with 1-bromoadamantane. The novel alkylcyclopentadienes have been converted to ferrocenes and molybdenum complexes of the type [CpRMo(CO)3CH3]. (2R)- 2,5,5-Trimethylbicyclo[2.2.1]hept-2-ylcyclopentadiene with an optical purity of 78% ee (the optical purity of the starting material fenchol) was converted into an optically active titanocene dichloride and tested in the catalytic hydrogenation of 2-phenyl-1-butene. The hydrogenation product was obtained with 31% ee, which compares favorably with results obtained with other group 4 metallocene dichlorides with one optically active alkyl substituent on each ring ligand. Facile procedures for the synthesis of the starting compounds exo-bornyl chloride and exo-fenchyl bromide based on the tosylate method have been developed with a tosylate melt or with toluene serving as solvents. Graphical Abstract Formation of Quaternary Stereogenic Centers by Wagner-Meerwein Rearrangement – Synthesis of Optically Active Cyclopentadienyl Complexes from Borneol and Fenchol

The 13 C, 69/71 Ga and 115 In NMR spectra of lithium tetra(tert-butyl)gallate and -indate were measured under various conditions. It proved possible to determine for the first time the coupling constants 1 J( 69/71 Ga, 13 C) = 182 Hz/232 Hz and 1 J( 115 In, 13 C) = 310±10 Hz for these metallates under conditions for solvent-separated ions. DFT calculations [B3LYP/6-311+G(d,p)] were carried out for organogallium compounds such as tri(tert-butyl)gallium, trimethylgallium and tetramethylgallate in order to predict and confirm coupling constants 1 J(Ga, 13 C). Graphical Abstract 69/71 Ga and 115 In NMR Spectroscopy of Lithium Tetra(tert-butyl)gallate and -indate: Spin-Spin Coupling Constants 1 J( 69/71 Ga, 13 C) and 1 J( 115 In, 13 C)

Reactions of di(alkyn-1-yl)(chloro)silanes, HSi(Cl)(C ≡ C-R)2, R 1 Si(Cl)(C ≡ C-R)2 or HSi(Cl)-(C ≡ C-R)C ≡ C-Rʹ, with an excess of triethylborane, BEt3, proceed slowly (several days) at 100 -120 °C. Twofold 1,1-organoboration of HSi(Cl)(C ≡ C-R)2 or HSi(Cl)(C ≡ C-R)C ≡ C-Rʹleads tosiloles, independent of R = n Bu, t Bu, SiMe 3 . This provides the most straightforward way to silolesbearing both a hydrogen and a chlorine at the silicon atom. However, in the cases of R = Ph, BEt 3 actsas 1,2-hydroborating reagent in the intermolecular first step of the reaction, leading to 1-silacyclobutene derivatives. All siloles and 1-silacyclobutene derivatives were characterized by multinuclear NMR spectroscopy ( 1 H, 11B, 13C and 29Si). Comparable 1-silacyclobutene derivatives were formed using 9-borabicyclo[3.3.1]nonane, 9-BBN, as a well established 1,2- hydroborating reagent Graphical Abstract Reactivity of Triethylborane towards Di(alkyn-1-yl)(chloro)silanes. Competition between 1,1-Organoboration and 1,2-Hydroboration

Adduct compounds of the general composition (MCl 5 ) 2 (β -P 4 Ch 4 ), M = Nb, Ta and Ch = S, Se, were obtained from solutions of M 2 Cl 10 and P 4 Ch 3 in CS 2 / n-hexane. The compounds are isotypic with (NbCl 5 ) 2 (β -P 4 S 4 ), crystallizing in the monoclinic space group P 2 1 /n (no. 14) with Z = 4. The lattice constants are a = 6.304(2), b = 13.071(3), c = 26.552(6) Å , β = 93.74(3)◦, V = 2183(1) Å 3 for (TaCl 5 ) 2 (β -P 4 S 4 ), a = 6.360(2), b = 13.322(3), c = 26.710(6) Å , β = 93.81(3) 0 , V = 2258(1) Å 3 for (TaCl 5 ) 2 (β -P 4 Se 4 ), and a = 6.334(2), b = 13.267(6), c = 26.583(7) Å , β = 93.71(3) 0 , V = 2229(2) Å 3 for (NbCl 5 ) 2 (β -P 4 Se 4 ). The adduct molecules consist of two MCl 5 units which are linked with two of the basal phosphorus atoms of the central β -P 4 Ch 4 cage. Graphical Abstract Adduct Compounds (MCl 5 ) 2 (β-P 4 Ch 4 ) with M = Nb, Ta and Ch = S, Se

The reactions of 1,1-diamino-2,2-diphenyl-substituted diphosphines featuring various degrees of P-P bond polarization with different alkynes were investigated. All diphosphines reacted with alkynes carrying one or two electron withdrawing carboxylic ester moieties under cleavage of the P-P bond and stereospecific phosphinyl-phosphination at the triple bond to give unsymmetrical ethane-1,2- bisphosphines. Several of the products were further converted into chelate complexes upon reaction with group-10 metal dihalides. All isolated compounds were characterized by analytical and spectroscopic data, and several of the new ligands and complexes by single-crystal X-ray diffraction studies. Graphical Abstract Activation of Polarized Phosphorus–Phosphorus Bonds by Alkynes: Rational Synthesis of Unsymmetrical 1,2-Bisphosphine Ligands and Their Complexes

Hydrolytic cleavage of the P-chlorophosphaalkenes (RMe2Si)2C=PCl (R = Me: 1a; R = iPr: 1b) in the presence of triethylamine leads to di(phosphavinyl) ethers (2,4-diphospha-3-oxapentadienes) [(RMe2Si)2C=P]2O (2a, 2b) as main products, accompanied by alkylphosphinic acids (RMe2Si)2(H)CP(H)(O)OH (3a, 3b). The hydrolysis of (PhMe2Si)2C=PCl (1c) proceeds less selectively. Reactions with metal oxides under aprotic conditions provide 2a [impure, from 1a with (nBu3Sn)2O] and 2b [from iodophosphaalkene (iPrMe2Si)2C=PI with Ag2O] as oils. 1H, 13C, 29Si and 31P NMR spectra, however, allow unambiguous characterisation of 2a and 2b. Formation mechanisms, structure, and C=P-O π stabilisation of the oxabisphosphaalkene [(H3Si)2C=P]2O (2ʹ) were studied with DFT methods. The double [2+4] cycloaddition reaction of 2a with two equivalents of cyclopentadiene leads to the phosphinous anhydride 7 as a mixture of diastereomers whereas the addition of two equivalents of tetrachloro-o-benzoquinone proceeds in a diastereoselective fashion. An X-ray crystal structure determination of the resulting oxo-bridged bis(2-phospha-2,5-dioxa-3,4-benzophospholene) derivative 8 revealed the presence of a racemic mixture of (R,R)- and (S,S)-configurated molecules. The solid state structure of a by-product, bisylphosphonic tetrachlorocatechol monoester (Me3Si)2CH-P(=O)(OH)-o-OC6Cl4OH 9, was also determined crystallographically. Graphical Abstract Di(phosphavinyl) Ethers (2,4-Diphospha-3-oxapentadienes)

The reaction of (F 3 C)Cl 2 SiCl 3 with the lithiated hydrazine LiN(Me)NMe 2 gives the compound (F 3 C)Cl 2 SiN(Me)NMe 2 (1) and in traces Cl 3 SiN(Me)NMe 2 (2). The reactions with LiN(SiMe 3 )NMe 2 and LiONMe 2 give (F 3 C)Cl 2 SiN(SiMe 3 )NMe 2 (4) and (F3C)Cl 2 SiONMe 2 (5), respectively. The compounds were characterised by multinuclear solution NMR, gas-phase IR spectroscopy and mass spectrometry. Information about conformational preferences of 1 and 4 can be extracted by comparing experimental IR spectra with those calculated by quantum chemical methods (B 3 LYP/6-311G**). The former show the gas phase of the β -donor-acceptor silanes 1 and 4 to be dominated by the anti conformations, while the calculations show a preference for the gauche conformers. The crystal structure of Cl 3 SiN(Me)NMe 2 (2) has been determined. The solid-state structures of the Ruppert reagent F 3 C-SiMe 3 (1) and its chlorine analogue F 3 C-SiCl 3 (2) have also been determined by X-ray diffraction of single crystals grown by in situ techniques. Graphical Abstract Trifluoromethylated Compounds with SiNN and SiON Backbone, and the Crystal Structures of Trimethyl- and Trichloro(trifluoromethyl)silane

1,4,7,10-Tetraazacyclododecane (1) reacts with allylbromide and 3-butenylbromide giving 1,4,7,10-tetraallyl-1,4,7,10-tetraazacyclododecane (TAC) (2a) and 1,4,7,10-tetra-3-butenyl-1,4,7,10- tetraazacyclododecane (TBC) (2b), respectively. Compounds 2a and 2b react with FeCl 2 , CoCl 2 , RhCl 3 , NiCl 2 , CuBr 2 , and TmCl 3 forming the complexes [FeCl(TAC)]Cl (3a), [FeCl(TBC)]Cl (3b), [CoCl(TAC)]Cl (4), [RhCl(TAC)]Cl 2 (5), [NiCl(TAC)]Cl (6a), [NiCl(TBC)]Cl (6b), [CuBr(TAC)]Br (7), [TmCl(TAC)]Cl 2 (8a), and [TmCl(TBC)]Cl 2 (8b). The reaction of 6a with an excess of CuCl affords a coordination polymer in which [NiCl(TAC)] + cations are connected by [Cu 6 Cl 8 ] 2 − anions (9). The 1 H and 13 C NMR spectra of 2a, 2b, 5, and 6a, as well as the single crystal X-ray structures of 2a ・ 3HCl, 6a, 6b, 7, and 9 are reported and discussed. Graphical Abstract Übergangsmetall- und Lanthanoid-Komplexe von 1,4,7,10-Tetraallylund 1,4,7,10-Tetra-3-butenyl-1,4,7,10-tetraazacyclododecan

5-[Amino(thiomethyl)methylene]-2,2-dimethyl-1,3-dioxane-4,6-dione (4) is obtained from 5-[bis- (thiomethyl)methylene]-2,2-dimethyl-1,3-dioxane-4,6-dione (1) and aqueous ammonia in excellent yield. Its reaction with m-chloroperbenzoic acid gives the sulfoxide derivative 5-[amino(sulfinylmethyl) methylene]-2,2-dimethyl-1,3-dioxane-4,6-dione (5). With triphenylphosphine, 5 reacts to give triphenyl( thiomethyl)phosphonium 5-cyano-2,2-dimethyl-1,3-dioxane-4,6-dionate (6) from which the methyltriphenylphosphonium salt 6a is obtained with excess triphenylphosphine. The crystal structures of 4, 5 and 6a are discussed. Graphical Abstract Synthesis and Reactions of 5-[Amino(thiomethyl)methylene]- 2,2-dimethyl-1,3-dioxane-4,6-dione

1,3-Dimethyl-5-bis(thiomethyl)methylenebarbituric acid (8) is obtained from 1,3-dimethylbarbituric acid and CS 2 /NEt 3 followed by alkylation with methyl iodide. Compound 8 reacts with aqueous ammonia to give 5-amino(thiomethyl)methylene-1,3-dimethylbarbituric acid (9). With benzylamine, the thiomethyl substituent in 9 is replaced to give 5-amino(benzylamino)methylene-1,3- dimethylbarbituric acid (10) while with methanesulfonic acid the sulfonate salt 11 is formed. The crystal structures of 8 and 9 are reported. Graphical Abstract Synthesis, Structure and Reactions of 1,3-Dimethyl-5-bis(thiomethyl)methylenebarbituric Acid

The title compounds have been synthesized by adding hydrogen peroxide to an aqueous solution of A 2 [Pt(CN) 4 ] (A = K, Rb, Cs). They grow as yellow needles after concentrating and cooling to 4 °C. The structures were elucidated from single crystal analysis. The isostructural compounds crystallize monoclinically, in space group C2/c with Z = 4. K 2 Pt(CN) 4 ·H 2 O 2 : a = 13.3751(7), b = 11.2713(6), c = 6.5461(3) Å, β = 105.432(1)◦, V = 951.3(3) Å 3 . Rb 2 Pt(CN) 4 ·H 2 O 2 : a = 13.6103(2), b = 11.6759(1), c = 6.5683(7) Å, β = 106.588(2) 0 , V = 1000.3(2) Å 3 . Cs 2 Pt(CN) 4 ·H 2 O 2 : a = 13.9569(2), b = 12.2023(2), c = 6.5857(9) Å, β = 107.590(3) 0 , V = 1069.1(2) Å 3 . As a remarkable feature, the hydrogen bonds O-H···N vary significantly with the cation size: in the Cs compound the O-H bonds are weakest, and the N· · ·H interactions are strongest. All three compounds were characterized by differential thermal analysis, thermogravimetry and infrared spectroscopy. Graphical Abstract New Hydrogen Peroxide Adducts of Alkali Metal Tetracyanoplatinates A 2 [Pt(CN) 4 ] ·H 2 O 2 (A = K, Rb, Cs)

Dimethyl(thioacetato)tin chloride (1) was synthesized by the reaction of dimethyltin dichloride with thioacetic acid in the presence of triethylamine. Compound 1 was subjected to hydrolysis under different reaction conditions in order to obtain sulfido/hydrosulfidotin compounds. Except for one case where the product was hexamethyl-1,3,5-trithia-2,4,6-tristannacyclohexane, (Me2SnS)3 (4), all other reactions led to desulfurization, and the products obtained were organostannoxane compounds, dinuclear tetramethyl-oxo-dichloroditin, { Me 2 SnCl 2 .Me 2 SnO } 2 (2), and tetraacetatodioxotetra( dimethyltin), (Me 2 Sn) 4 O 2 (O 2 CMe) 4 (3). These complexes have been characterized by 1 H, 13 C, 119 Sn NMR and FTIR spectroscopy, and compounds 2 - 4 also by X-ray crystallography. Density functional calculations were performed to explain the structure and reactivity of the compounds. Graphical Abstract Synthesis, Characterization and Reactivity of a Diorganotin Thiocarboxylate: Dimethyl(thioacetato)-tin(IV) Chloride and its Reactions with Nucleophiles Exhibiting Desulfurization

Five chiral β -aminothioethers were obtained via different routes orientated on literature protocols. Three of these β -aminothioethers were reacted with two di-μ-chloro-bis { chloro[η 6 -arene]- ruthenium(II) } derivatives, resulting in the title complex salts. The complex cations exhibit three stereocenters, viz. ruthenium and sulfur atoms and the chiral benzylic carbon atom of the chelate ligand backbone. Both, ruthenium and sulfur stereocenters epimerize into a mixture of four NMR distinguishable diastereomers in equilibrium, but the designed chiral benzylic carbon atom is stable under all conditions applied so far. The relative diastereomer concentrations in solution depend mainly on the spatial requirements of the η 6 -arene ligand rather than on the thioether moiety. Diastereomer ratios and the absolute configurations in solution were studied by NMR and CD spectroscopy. The spectroscopic results fit to the absolute X-ray crystal structure parameters determined for the diastereomers present in the crystalline state. Graphical Abstract Configurational Flexibility of Epimeric β-Aminothioether-chelated Ruthenium(II) η 6 -Arene Complex Salts

The dimer [(η 5 -C 5 Me 5 )Ru(C 3 B 2 Me 5 )RhCl] 2 (2) reacts with 1,2-bis(diphenylphosphino)ethane (dppe) to give the triple-decker complex [(η 5 -C 5 Me 5 )Ru(C 3 B 2 Me 5 )Rh- (dppe)Cl] (3). Its constitution follows from NMR and MS data, and a single-crystal X-ray diffraction study. Graphical Abstract Synthesis and Crystal Structure of the Triple-decker Complex [(η 5 -C 5 Me 5 )- Ru(μ,η 5 -1,3-C 3 B 2 Me 5 )RhCl- (Ph 2 PCH 2 ) 2 ]