Synthesis of a “Masked” Terminal Nickel(II) Sulfide by Reductive Deprotection and its Reaction with Nitrous Oxide

The addition of 1 equiv of KSCPh₃ to [L^RNiCl] (L^R={(2,6‐iPr₂C₆H₃)NC(R)}₂CH; R=Me, tBu) in C₆H₆ results in the formation of [L^RNi(SCPh₃)] ( 1 : R=Me; 2 : R=tBu) in good yields. Subsequent reduction of 1 and 2 with 2 equiv of KC₈ in cold (?25 °C) Et₂O in the presence of 2 equiv of 18‐crown‐6 results in the formation of “masked” terminal Ni^II sulfides, [K(18‐crown‐6)][L^RNi(S)] ( 3 : R=Me; 4 : R=tBu), also in good yields. An X‐ray crystallographic analysis of these complexes suggests that they feature partial multiple‐bond character in their Ni? S linkages. Addition of N₂O to a toluene solution of 4 provides [K(18‐crown‐6)][L^tBuNi(SN?NO)], which features the first example of a thiohyponitrite (κ²‐[SN?NO]^2?) ligand.     

Die Bildung von [(tBu)2P]2P?P[P(tBu)2]2 aus LiP[P(tBu)2]2 und 1,2-Dibromethan. Die Thermolyse von tBu2P?PP(Br)tBu2

[(tBu)₂P]₂P? P[P(tBu)₂]₂ from LiP[P(tBu)₂]₂ and 1,2-Dibromomethane. Pyrolysis of tBu₂P? P?P(Br)tBu₂ All products of the reaction of [tBu₂P]₂PLi 1 with 1,2-dibromoethane 2 were investigated. Already at ?70°C tBu₂P? P?P(Br)tBu₂ 3 as main product and [tBu₂P]₂PBr 4 are formed. Only with an excess of 1 also [tBu₂P]P? P[P(tBu)₂]₂ 5 is obtained. Warming of a pure solution of 3 in toluene from ?70°C to ?30°C leads to 4 , and at 20°C tBu₂PBr and the cyclophosphanes P₄[P(tBu)₂]₄ and P₃[P(tBu)₂]₃ are observed. 5 does not result from 3 , it's rather a byproduct from the reaction of 1 with 4 . Also the ylide 3 and 1 yields 5 .     

Lanthanide(II) Complexes of the Dihydrotriazinido Ligand [N{C(Ph)=N}2C(tBu)Ph]−

The potassium dihydrotriazinide K(L^Ph,tBu) ( 1 ) was obtained by a metal exchange route from [Li(L^Ph,tBu)(THF)₃] and KOtBu (L^Ph,tBu = [N{C(Ph)=N}₂C(tBu)Ph]). Reaction of 1 with 1 or 0.5 equivalents of SmI₂(thf)₂ yielded the monosubstituted Sm^II complex [Sm(L^Ph,tBu)I(THF)₄] ( 2 ) or the disubstituted [Sm(L^Ph,tBu)₂(THF)₂] ( 3 ), respectively. Attempted synthesis of a heteroleptic Sm^II amido‐alkyl complex by the reaction of 2 with KCH₂Ph produced compound 3 due to ligand redistribution. The Yb^II bis(dihydrotriazinide) [Yb(L^Ph,tBu)₂(THF)₂] ( 4 ) was isolated from the 1:1 reaction of YbI₂(THF)₂ and 1 . Molecular structures of the crystalline compounds 2 , 3· 2C₆H₆ and 4· PhMe were determined by X‐ray crystallography.     

Synthesis and Thermolysis of the Homoleptic Iron(II) Complex [Fe{cyclo‐(P5tBu4)}2]

Na[cyclo‐(P₅tBu₄)] ( 1 ) reacts with [FeBr₂(CO)₄] (2:1) to give the first homoleptic iron(II) complex [Fe{cyclo‐(P₅tBu₄)}₂] ( 2 ) containing two tridentate cyclo‐(P₅tBu₄)^– ligands. Thermolysis of 2 up to 500 °C produces a new phosphorus‐rich iron phosphide, calculated as FeP₆ according to the mass change.     

Reaktionen von (tBu)2P?PP(Br)tBu2 mit LiP(SiMe3)2, LiPMe2 und LiMe,LitBu, LinBu

Reactions of (tBu)₂P? P?P(Br)tBu₂ with LiP(SiMe₃)₂, LiPMe₂ and LiMe, LitBu and LinBu The reactions of (tBu)₂P? P?P(Br)tBu₂ 1 with LiP(SiMe₃)₂ 2 yield (Me₃Si)₂P? P(SiMe₃)₂ 4 and P[P(tBu)₂]₂P(SiMe₃)₂ 5 , whereas 1 with LiPMe₂ 2 yields P₂Me₄ 6 and P[(tBu)₂]₂PMe₂ 7 . 1 with LiMe yields the ylid tBu₂P? P?P(Me)tBu₂ (main product) and [tBu₂P]₂PMe 15 . In the reaction of 1 with tBuLi [tBu₂P]₂PH 11 is the main product and also tBuP? P?P(R)tBu₂ 21 is formed. The reaction of 1 with nBuLi leads to [tBu₂P]₂PnBu 17 (main product) and tBu₂P? P?P(nBu)tBu₂ 22 (secondary product).     

Neutral and Anionic Monomeric Zirconium Imides Prepared via Selective C=N Bond Cleavage of a Multidentate and Sterically Demanding β‐Diketiminato Ligand

A sterically encumbering multidentate β‐diketiminato ligand, ^tBuL2 (^tBuL2=[ArNC(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂NMe₂]^?, Ar=2,6‐iPr₂C₆H₃), is reported in this study along with its coordination chemistry to zirconium(IV). Using the lithio salt of this ligand, Li(^tBuL2) ( 4 ), the zirconium(IV) precursor (^tBuL2)ZrCl₃ ( 6 ) could be readily prepared in 85 % yield and structurally characterized. Reduction of 6 with 2 equiv of KC₈ resulted in formation of the terminal and mononuclear zirconium imide‐chloride [C(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂NMe₂]Zr(=NAr)(Cl) ( 7 ) as the result of reductive C=N cleavage of the imino fragment in the multidentate ligand ^tBuL2 by an elusive Zr^II species (^tBuL2)ZrCl ( A ). The azabutadienyl ligand in 7 can be further reduced by 2 e^? with KC₈ to afford the anionic imide [K(THF)₂]{[CH(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂N(Me)CH₂]Zr=NAr} ( 8‐2THF ) in 42 % isolated yield. Complex 8‐2THF results from the oxidative addition of an amine C?H bond followed by migration to the vinylic group of the formal [C(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂NMe₂]^? ligand in 7 . All halides in 6 can be replaced with azides to afford (^tBuL2)Zr(N₃)₃ ( 9 ) which was structurally characterized, and reduction with two equiv of KC₈ also results in C=N bond cleavage of ^tBuL2 to form [C(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂NMe₂]Zr(=NAr)(N₃) ( 10 ), instead of the expected azide disproportionation to N^3? and N₂. Solid‐state single crystal structural studies confirm the formation of mononuclear and terminal zirconium imido groups in 7 , 8‐Et₂O , and 10 with Zr=NAr distances being 1.8776(10), 1.9505(15), and 1.881(3) Å, respectively.     

Neodymium(III) Complexes Capable of Multi‐Electron Redox Chemistry

A family of neodymium complexes featuring a redox‐active ligand in three different oxidation states has been synthesized, including the iminoquinone (L⁰) derivative, (^dippiq)₂NdI₃ ( 1‐iq ), the iminosemiquinone (L¹⁻) compound, (^dippisq)₂NdI(THF) ( 1‐isq ), and the amidophenolate (L²⁻) [K(THF)₂][(^dippap)₂Nd(THF)₂] ( 1‐ap ) and [K(18‐crown‐6)][(^dippap)₂Nd(THF)₂] ( 1‐ap crown ) species. Full spectroscopic and structural characterization of each derivative established the +3 neodymium oxidation state with redox chemistry occurring at the ligand rather than the neodymium center. Oxidation with elemental chalcogens showed the reversible nature of the ligand‐mediated reduction process, forming the iminosemiquinone metallocycles, [K(18‐crown‐6)][(^dippisq)₂Nd(S₅)] ( 2‐isq crown ) and [K(18‐crown‐6)(THF)][(^dippisq)₂Nd(Se₅)] ( 3‐isq crown ), which are characterized to contain a 6‐membered twist‐boat ring.     

Cations Controlling the Chiral Assembly of Luminescent Atomically Precise Copper(I) Clusters

Chiral assembly and asymmetric synthesis are critically important for the generation of chiral metal clusters with chiroptical activities. Here, a racemic mixture of [K(CH₃OH)₂(18‐crown‐6)]⁺[Cu₅(S^tBu)₆]^? ( 1?CH₃OH ) in the chiral space group was prepared, in which the chiral red‐emissive anionic [Cu₅(S^tBu)₆]^? cluster was arranged along a twofold screw axis. Interestingly, the release of the coordinated CH₃OH of the cationic units turned the chiral 1?CH₃OH crystal into a mesomeric crystal [K(18‐crown‐6)]⁺[Cu₅(S^tBu)₆]^? ( 1 ), which has a centrosymmetric space group, by adding symmetry elements of glide and mirror planes through both disordered [Cu₅(S^tBu)₆]^? units. The switchable chiral/achiral rearrangement of [Cu₅(S^tBu)₆]^? clusters along with the capture/release of CH₃OH were concomitant with an intense increase/decrease in luminescence. We also used cationic chiral amino alcohols to induce the chiral assembly of a pair of enantiomers, [d /l ‐valinol(18‐crown‐6)]⁺[Cu₅(S^tBu)₆]^? ( d /l ‐Cu_5V ), which display impressive circularly polarized luminescence (CPL) in contrast to the CPL‐silent racemic mixture of 1?CH₃OH and mesomeric 1 .     

Cyclopentadienyl Dicarbonyl Iron‐Bismuth Compounds – Synthesis,Structure, and Reactivity

Abstract. The cyclopentadienyl‐substituted iron‐bismuth complexes [{Cp(CO)₂Fe}BiCl₂] ( 1 ), [{Cp(CO)₂Fe}BiBr₂] ( 2 ), [{Cp′′(CO)₂Fe}BiBr₂] ( 3 ) and [{Cp*(CO)₂Fe}BiBr₂] ( 4 ) were prepared with high yields starting from [Cp^x(CO)₂Fe]₂ [Cp^x = C₅H₅ (Cp), C₅H₃‐1, 3‐tBu₂ (Cp′′), C₅Me₅ (Cp*)] and the corresponding bismuth halides. The single crystal X‐ray structure analyses of compounds 2 – 4 are reported. Comparison of their solubility demonstrates that the steric hindrance in this type of compounds is only slightly higher for compound 3 compared with compound 2 but significantly lower compared with the Cp* derivative 4 . Compounds 1 – 4 react with nucleophililic reagents such as KOtBu, NaOCH₂CH₂OCH₃, and NaOSiMe₃ as well as with water in the presence of an amine to give a mixture of [{Cp^x(CO)₂Fe}BiX] (X = Cl, Br) and [{Cp^x(CO)₂Fe}₃Bi]. In case of a reaction with nBu₄NCl and DMAP (dimethylaminopyridine) no such dismutation is observed. Instead the complexes [{Cp(CO)₂Fe}BiBr₂(DMAP)₂] ( 5 ), [NnBu₄]₂[{{Cp(CO)₂Fe}BiBr₃}₂] ( 6 ) and [NnBu₄]₂[{{Cp(CO)₂Fe}BiCl₃}₂] ( 7 ) were isolated and characterized by single‐crystal X‐ray diffraction.     

Facile synthesis of zwitterionic organoaluminum complexes containing formally dianionic homoscorpionate ligands

A series of zwitterionic aluminum complexes of the type AlX[(2‐O‐3,5‐tBu₂C₆H₂)₃PZ] (AlX [O₃PZ]; X = Cl, Me, Et, and iBu; Z = H, Me) containing C₃‐symmetric, formally dianionic, facially tridentate ligands [O₃PZ]^2? were prepared and structurally characterized. Although serendipitous, these complexes can be readily synthesized by partial protonolysis of AlX₃ with equal molar (2‐HO‐3,5‐tBu₂C₆H₂)₃P (H₃[O₃P]) or [(2‐HO‐3,5‐tBu₂C₆H₂)₃p.m.e](OTf) ({H₃[O₃PMe]}OTf) in THF at 25°C or elevated temperatures. Alcoholysis of AlMe[O₃PMe] ( 2 ) with an excess amount of MeOH in refluxing toluene generates AlOMe[O₃PMe] ( 10 ). Salt metathesis of AlCl[O₃PMe] ( 6 ) with nBuM (M = Li, MgCl) and NaOR (R = tBu, Ph) in ethereal solutions affords AlnBu[O₃PMe] ( 9 ) and AlOR[O₃PMe] (R = tBu ( 11 ), Ph ( 12 )), respectively. Reactivity of 10 , 11 , and 12 with respect to catalytic ring‐opening polymerization of ε‐caprolactone is assessed.     

Synthese und Eigenschaften der Di‐tert‐butylphosphide [M(PtBu2)2]2 (M = Zn,Hg) und [Cu(PtBu2)]4

Syntheses and Properties of Di‐tert‐butylphosphides [M(PtBu₂)₂]₂ (M = Zn, Hg) and [Cu(PtBu₂)]₄ The phosphides [M(PtBu₂)₂]₂ (M = Zn, Hg) and [Cu(PtBu₂)]₄ are accessible from reaction of LiPtBu₂ with ZnI₂, HgCl₂ and CuCl, respectively. [M(PtBu₂)₂]₂ (M = Zn, Hg) are dimers in the solid state. X‐ray structural analyses of these phosphides reveal that [M(PtBu₂)₂]₂ (M = Zn, Hg) contain four‐membered M₂P₂‐rings whereas [Cu(PtBu₂)]₄ features a planar eight‐membered Cu₄P₄‐ring. Degradation reaction of LiPtBu₂(BH₃) in the presence of HgCl₂ results in the dimeric phosphanylborane BH₃ adduct [tBu₂PBH₂(BH₃)]₂. X‐ray quality crystals of [tBu₂PBH₂(BH₃)]₂ (monoclinic, P2₁/n) are obtained from a pentane solution at 6 °C. According to the result of the X‐ray structural analysis, the O₂‐oxidation product of [Hg(PtBu₂)₂]₂, [Hg{OP(O)(tBu)OPtBu₂}(μ‐OPtBu)]₂, features in the solid state structure two five‐membered HgP₂O₂‐rings and a six‐membered Hg₂P₂O₂‐ring. Herein the spiro‐connected Hg atoms are member of one five‐membered and of the six‐membered ring.     

Synthesis,Spectroscopy, and Hydroformylation Activity of Sterically Demanding,Phosphite‐Modified Cobalt Catalysts

The dinuclear complex [Co₂(CO)₆{P(O‐2,4‐t‐Bu₂C₆H₃)₃}₂] ( 6 ) has been synthesised and fully characterised. X‐Ray crystal‐structure analysis revealed a trans‐diaxial geometry, no bridging carbonyls, and Co? Co and Co? P bond lengths of 2.706(5) and 2.134(4) Å, respectively. The hydroformylation of pent‐1‐ene in the presence of 6 was studied at 120–180° at pressures between 20 and 80 bar Syngas. High‐pressure (HP) spectroscopy (IR, NMR) was used to detect potential hydride intermediates. HP‐IR Studies revealed the formation of [CoH(CO)₃{P(O‐2,4‐t‐Bu₂C₆H₃)₃}] ( 2 ) at ca. 105°, with no significant amount of [CoH(CO)₄] detectable. The intermediate 2 was synthesised and characterised. The formation of the undesired complex [CoH(CO)₂{P(O‐2,4‐t‐Bu₂C₆H₃)₃}₂] was completely suppressed due to the large cone angle of the sterically demanding phosphite.     

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.     

Pivaloylmetals (tBu‐COM: M=Li,MgX, K) as Equilibrium Components

Short‐lived pivaloylmetals, (H₃C)₃C‐COM, were established as the reactive intermediates arising through thermal heterolytic expulsion of O=CtBu₂ from the overcrowded metal alkoxides tBuC(=O)‐C(‐OM)tBu₂ (M=MgX, Li, K). In all three cases, this fission step is counteracted by a faster return process, as shown through the trapping of tBu‐COM by O=C(tBu)‐C(CD₃)₃ with formation of the deuterated starting alkoxides. If generated in the absence of trapping agents, all three tBu‐COM species “dimerize” to give the enediolates MO‐C(tBu)=C(tBu)‐OM along with O=CtBu₂ (2 equiv). A common‐component rate depression by surplus O=CtBu₂ proves the existence of some free tBu‐COM (separated from O=CtBu₂); but companion intermediates with the traits of an undissociated complex such as tBu‐COM & O=CtBu₂ had to be postulated. The slow fission step generating tBu‐COMgX in THF levels the overall rates of dimerization, ketone addition, and deuterium incorporation. Formed by much faster fission steps, both tBu‐COLi and tBu‐COK add very rapidly to ketones and dimerize somewhat slower (but still fairly fast, as shown through trapping of the emerging O=CtBu₂ by H₃CLi or PhCH₂K, respectively). At first sight surprisingly, the rapid fission, return, and dimerization steps combine to very slow overall decay rates of the precursor Li and K alkoxides in the absence of trapping agents: A detailed study revealed that the fast fission step, generating tBu‐COLi in THF, is followed by a kinetic partitioning that is heavily biased toward return and against the product‐forming dimerization. Both tBu‐COLi and tBu‐COK form tBu‐CH=O with HN(SiMe₃)₃, but only tBu‐COK is basic enough for being protonated by the precursor acyloin tBuC(=O)‐C(‐OH)tBu₂.     

Trinuclear Phosphaferroles from Alkylidyne‐Phosphaalkyne Coupling Reactions

Reaction of bisalkylidyne cluster compounds [Fe₃(CO)₉(μ₃‐CR)₂] ( 1a—d ) ( a , R = H; b , R = F; c , R = Cl; d , R = Br) with the phosphaalkyne t‐C₄H₉‐C≡P ( 2 ) yield a single isomer of the phosphaferrole cluster [Fe₃(CO)₈][CR‐C(t‐Bu)‐P‐CR] ( 3a—d ). However, the three isomeric compounds [Fe₃(CO)₈][C(OEt)‐C(t‐Bu)‐P‐C(Me)] ( 5a ), [Fe₃(CO)₈][C(Me)‐C(t‐Bu)‐P‐C(OEt)] ( 5b ), and [Fe₃(CO)₈][C(OEt)‐C(Me)‐C(t‐Bu)‐P] ( 5c ) are obtained in the reaction of [Fe₃(CO)₉(μ₃‐CMe)(μ₃‐C‐OEt)] ( 4 ) with 2 . As the phosphaferroles 3 possess a lone pair of electrons at the phosphorus atom they can act as ligands. [Fe₃(CO)₈][CF‐C(t‐Bu)‐P‐CF]ML_n ( 7a—c ) ( a , ML_n = Cr(CO)₅; b , ML_n = CpMn(CO)₂; c , ML_n = Cp^*Mn(CO)₂) were formed from 3b and L_nM(η²‐C₈H₁₄) ( 6a—c ). The dinuclear cluster [Fe₂(CO)₆][CF‐CF‐C(t‐Bu)‐PH(OMe)] ( 8 ) was obtained from 3b and NiCl₂·6H₂O in methanol. The structures of 3a—d , 5a—c , 7b , and 8 have been elucidated by X‐ray crystal structure determinations.     

Reactions of Tri‐tert‐butylazadiboriridine NB2R3 with Carbonyl and Similar Species

The carbonyl group of X(R')CO is added to the B—B bond of the three‐membered ring compound NB₂R₃ ( 1 ; R = tBu) to give the five‐membered rings [—BR—NR—BR—X(Rapos;)C—O—] ( 2a — d ; Rapos;/X = tBu/H, Ph/Ph, H/OMe, H/NMe₂). The tetraazoniatetraboratatricyclo[6.2.0.0^{3, 6}]deca‐2, 4, 7, 9‐tetraenes N₄B₄C₂R₆Rapos;₂ ( 4a , b ; Rapos; = Me, Et), known products from the reaction of 1 with isonitriles CNRapos;, undergo a rearrangement to give the corresponding deca‐1, 4, 6, 9‐tetraenes 6a , b by the migration of two tBu groups from boron to carbon on photolysis; the structure of 6a is confirmed by X‐ray analysis. The reaction of CO, generated from carbonylmetal complexes (photolytically from [Cr(CO)₆] or [Cp₂Fe₂(CO)₄]; thermally from [Fe₂(CO)₉] or [Co₂(CO)₈]), with 1 gives the 3, 7‐dioxonia‐1, 5‐diazonia‐2, 4, 6, 8‐tetraboratanaphtalene O₂N₂C₂B₄R₆ ( 7 ), as has been known from the reaction of [Fe(CO)₅] and 1 . The product 7 is also obtained from the isomeric dispiro compound 5 , the known product from the reaction of 1 with gaseous CO at —78 °C, by standing in solution at room temperature. Surprisingly, the reaction of 1 with CO from the photolysis of [CpMn(CO)₃] gives a naphthalene‐type isomer of 7 , the 1, 5‐dioxonia‐3, 7‐diazonia species 8 , the crystal structure of which is reported.     

Donor‐unsupported Phosphanylmethanides Li[CH2PR2] (R = tBu,Ph) – Crystal Structure of Li[CH2PtBu2] Solved by XRPD and DFT‐D Calculations

The solvent‐free methyllithium derivatives Li[CH₂PR₂] (R = tBu, Ph) were prepared via the reaction of CH₃PR₂ with Li[tBu]. It should be noted that the deprotonation of CH₃PtBu₂ with Li[tBu] occurred at 60 °C, whereas Li[CH₂PPh₂] was already formed from CH₃PPh₂ with Li[tBu] at ambient temperature. The structure determination of di‐tert‐butylphosphanylmethyllithium was performed by high resolution X‐ray powder diffraction analysis at different temperatures. This led to two possible structure solutions with similar quality criteria (space groups Iba2 and I2/a). Therefore CASTEP DFT‐D calculations were applied to verify the correct crystal structure. The solid‐state structure of di‐tert‐butylphosphanylmethyllithium consists of alternating edge‐sharing six‐ and four‐membered rings, which form a polymeric, infinite double‐chain along the crystallographic c axis in the monoclinic space group I2/a. Two Li[CH₂PtBu₂] units connected via an inversion center form a six‐membered Li₂C₂P₂ ring in the chair conformation. The nearly flat four‐membered Li₂C₂ ring, is oriented perpendicularly to the twofold axis.     

Komplexchemie P‐reicher Phosphane und Silylphosphane. XXII. Die Bildung von [η2‐{tBu–P=P–SiMe3}Pt(PR3)2]aus (Me3Si)tBuP–P=P(Me)tBu2 und [η2‐{C2H4}Pt(PR3)2]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XXII. The Formation of [η²‐{^tBu–P=P–SiMe₃}Pt(PR₃)₂] from (Me₃Si)^tBuP–P=P(Me)^tBu₂ and [η²‐{C₂H₄}Pt(PR₃)₂] (Me₃Si)^tBuP–P = P(Me)^tBu₂ reacts with [η²‐{C₂H₄}Pt(PR₃)₂] yielding [η²‐{^tBu–P=P–SiMe₃}Pt(PR₃)₂]. However, there is no indication for an isomer which would be the analogue to the well known [η²‐{^tBu₂P–P}Pt(PPh₃)₂]. The syntheses and NMR data of [η²‐{^tBu–P=P–SiMe₃}Pt(PPh₃)₂] and [η²‐{^tBu–P=P–SiMe₃}Pt(PMe₃)₂] as well as the results of the single crystal structure determination of [η²‐{^tBu–P=P–SiMe₃}Pt(PPh₃)₂] are reported.     

Structural and Electronic Effects of Stepwise Reduction of a Tetraaryl[3]Cumulene

The chemical reduction of a [3]cumulene ([3]TrTol) has been explored using alkali metals. Mono‐ and doubly reduced forms of [3]TrTol were isolated as solvent‐separated ion pairs with {Na(18‐crown‐6)THF₂}⁺ and {K(18‐crown‐6)THF₂}⁺ counterions and crystallographically characterized. This allowed analysis of structural parameters of the “naked” anions of [3]TrTol without interference from metal binding. The dianion of [3]TrTol was also isolated as a contact‐ion complex with {Cs(18‐crown‐6)}⁺ cations, thereby adding the effect of metal coordination to the core. Structural comparisons of anions to the neutral molecule, [3]TrTol, outline monotonic increases in bond‐length alternation (BLA) upon stepwise reduction. The greatest BLA value is found for the contact‐ion complex, which shows an alternating sequence of short and long carbon–carbon bonds, consistent with the structure of an alkyne. In contrast to studies on tetraphenyl[3]cumulene, the cumulenic framework of [3]TrTol remains planar in all the derivatives.     

Zur Reaktivität des Ferriophosphaalkens (Z)‐[Cp*(CO)2FeP=C(tBu)NMe2] gegenüber Propiolsäureestern HC≡C‐CO2R (R=Me,Et) und Acetylendicarbonsäureestern RO2C‐C≡C‐CO2R (R=Me,Et, tBu)

On the Reactivity of the Ferriophosphaalkene (Z)‐[Cp*(CO)₂Fe‐P=C(tBu)NMe₂] towards Propiolates HC≡C‐CO₂R (R=Me, Et) and Acetylene Dicarboxylates RO ₂C‐C≡C‐CO₂R (R=Me, Et, tBu) The reaction of equimolar amounts of (Z)‐[Cp*(CO)₂Fe‐P=C(tBu)NMe₂] 3 and methyl‐ and ethyl‐propiolate ( 2a, b ) or of 3 and dialkyl acetylene dicarboxylates 1a (R=Me), 1b (Et), 1c (tBu) afforded the five‐membered metallaheterocycles [Cp*(CO) =C(tBu)NMe₂] ( 4a, b ) and [Cp*(CO) =C(tBu)NMe₂] ( 5a—c ). The molecular structures of 4b and 5a were elucidated by single crystal X‐ray analyses. Moreover, the reactivity of 4b towards ethereal HBF₄ was investigated.