Uranocenium: Synthesis,Structure, and Chemical Bonding

Abstraction of iodide from [(η⁵‐C₅ⁱPr₅)₂UI] ( 1 ) produced the cationic uranium(III) metallocene [(η⁵‐C₅ⁱPr₅)₂U]⁺ ( 2 ) as a salt of [B(C₆F₅)₄]^?. The structure of 2 consists of unsymmetrically bonded cyclopentadienyl ligands and a bending angle of 167.82° at uranium. Analysis of the bonding in 2 showed that the uranium 5f orbitals are strongly split and mixed with the ligand orbitals, thus leading to non‐negligible covalent contributions to the bonding. Investigation of the dynamic magnetic properties of 2 revealed that the 5f covalency leads to partially quenched anisotropy and fast magnetic relaxation in zero applied magnetic field. Application of a magnetic field leads to dominant relaxation by a Raman process.     

Isolation of a Perfectly Linear Uranium(II) Metallocene

Reduction of the uranium(III) metallocene [(η⁵‐C₅ⁱPr₅)₂UI] ( 1 ) with potassium graphite produces the “second‐generation” uranocene [(η⁵‐C₅ⁱPr₅)₂U] ( 2 ), which contains uranium in the formal divalent oxidation state. The geometry of 2 is that of a perfectly linear bis(cyclopentadienyl) sandwich complex, with the ground‐state valence electron configuration of uranium(II) revealed by electronic spectroscopy and density functional theory to be 5f³ 6d¹. Appreciable covalent contributions to the metal‐ligand bonds were determined from a computational study of 2 , including participation from the uranium 5f and 6d orbitals. Whereas three unpaired electrons in 2 occupy orbitals with essentially pure 5f character, the fourth electron resides in an orbital defined by strong 7s‐6d mixing.     

Halbsandwichkomplexe des Iridiums mit Tetramethylcyclopentadienyl als Ringligand

Halfsandwich‐Type Complexes of Iridium with Tetramethylcyclopentadienyl as Ligand The iridium(I) complexes [(η⁵‐C₅HMe₄)Ir(C₂H₄)₂] ( 2 ) and [(η⁵‐C₅HMe₄)Ir(CO)₂] ( 4 ), which have been prepared from [IrCl(C₂H₄)₂]₂ or [IrCl(CO)₃]_n and LiC₅HMe₄, react with tosylchloride as well as with X₂ (X = Cl, Br, I) by oxidative addition to yield the corresponding iridium(III) compounds. Treating the complexes [(η⁵‐C₅HMe₄)IrX₂]_n ( 7 — 9 ) with CO or PR₃ leads to a cleavage of the halide bridges and to the formation of the mononuclear products [(η⁵‐C₅HMe₄)IrX₂(CO)] ( 10 , 11 ) and [(η⁵‐C₅HMe₄)IrX₂(PR₃)] ( 12 — 20 ), respectively. The molecular structure of [(η⁵‐C₅HMe₄)IrBr₂(PiPr₃)] ( 18 ) was determined crystallographically. The reactions of 8 (X = Br) and 9 (X = I) with Ph₂P(CH₂)_nPPh₂ (n = 1 or 2) afford the bridged compounds [{(η⁵‐C₅HMe₄)IrX₂}₂{μ‐Ph₂P(CH₂)_nPPh₂}] ( 21—23 ). The dihalide complexes [(η⁵‐C₅HMe₄)IrI₂(PPh₃)] ( 16 ) and [(η⁵‐C₅HMe₄)IrX₂(PiPr₃)] ( 17—19 ) react with hydride sources to give the dihydrido‐ and monohydrido derivatives [(η⁵‐C₅HMe₄)IrH₂(PPh₃)] ( 24 ) and [(η⁵‐C₅HMe₄)IrH(X)(PiPr₃)] ( 25—27 ). The related dimethyl and monomethyl compounds [(η⁵‐C₅HMe₄)Ir(CH₃)₂(PiPr₃)] ( 28 ) and [(η⁵‐C₅HMe₄)IrCH₃(I)(PiPr₃)] ( 29 ) have been obtained from the dihalide precursors 18 or 19 and CH₃MgI in the molar ratio of 1:2 or 1:1, respectively.     

[Ni(iPr2Im)2Br2]: A Convenient Entry into NHC Nickel ­Chemistry

The reaction of the NHC iPr₂Im [NHC=N‐heterocyclic carbene, iPr₂Im = 1, 3‐bis(isopropyl)imidazolin‐2‐ylidene] with freshly prepared NiBr₂ in thf or dme results in the formation of the air stable nickel(II) complex trans‐[Ni(iPr₂Im)₂Br₂] ( 2 ). Complex 2 was structurally characterized. Thermal analysis (DTA/TG) reveals a very high decomposition temperature of 298 °C. Reduction of 2 with sodium or C₈K in the presence of the olefins COD (cyclooctadiene) or COE (cyclooctene) affords the highly reactive compounds [Ni₂(iPr₂Im)₄(COD)] ( 1 ) and [Ni(iPr₂Im)₂(COE)] ( 4 ). Alkylation of 2 with organolithiums leads to the formation of trans‐[Ni(iPr₂Im)₂(R)₂] [R = Me ( 5 ), CH₂SiMe₃ ( 6 )], whereas the reaction of 2 with LiCp* [Cp* = (η⁵‐C₅(CH₃)₅)] at 80 °C causes the loss of one NHC ligand and affords [(η⁵‐C₅(CH₃)₅)Ni(iPr₂Im)Br] ( 7 ).     

Der Dihydridoiridium(III)‐Komplex [IrH2Cl(PiPr3)2] als Molekülbaustein für unsymmetrische Rhodium–Iridiumund Iridium–Iridium‐Zweikernverbindungen

The Dihydridoiridium(III) Complex [IrH₂Cl(P i Pr₃)₂] as a Molecular Building Block for Unsymmetrical Binuclear Rhodium–Iridium and Iridium–Iridium Compounds The title compound [IrH₂Cl(PiPr₃)₂] ( 3 ) reacts with the chloro‐bridged dimers [RhCl(PiPr₃)₂]₂ ( 1 ) and [IrCl(C₈H₁₄)(PiPr₃)]₂ ( 5 ) by cleavage of the Cl‐bridges to give the unsymmetrical binuclear complexes 4 and 6 with Rh(μ‐Cl)₂Ir and Ir(μ‐Cl)₂Ir as the central building block. The reactions of 3 with the bis(cyclooctene) and (1,5‐cyclooctadiene) compounds [MCl(C₈H₁₄)₂]₂ ( 7 , 8 ) and [MCl(η⁴‐C₈H₁₂)]₂ ( 9 , 10 ) (M = Rh, Ir) occur analogously and afford the rhodium(I)‐iridium(III) and iridium(I)‐iridium(III) complexes 11 – 14 in 70–80% yield. Treatment of [(η⁴‐C₈H₁₂)M(μ‐Cl)₂IrH₂(PiPr₃)₂] ( 13 , 14 ) with phenylacetylene leads to the formation of the substitution products [(η⁴‐C₈H₁₂)M(μ‐Cl)₂IrH(C≡CPh)(PiPr₃)₂] ( 15 , 16 ) without changing the central molecular core. Similarly, the compound [(η⁴‐C₈H₁₂)Rh(μ‐Br)₂IrH(C≡CPh)(PiPr₃)₂] ( 18 ) has been prepared; it was characterized by X‐ray crystallography.     

Charge Effects in PCP Pincer Complexes of NiII bearing Phosphinite and Imidazol(i)ophosphine Coordinating Jaws: From Synthesis to Catalysis through Bonding Analysis

This contribution reports on a new family of Ni^II pincer complexes featuring phosphinite and functional imidazolyl arms. The proligands ^RPIMC^HOP^R′ react at room temperature with Ni^II precursors to give the corresponding complexes [(^RPIMCOP^R′)NiBr], where ^RPIMCOP^R=κ^P,κ^C,κ^P‐{2‐(R′₂PO),6‐(R₂PC₃H₂N₂)C₆H₃}, R=iPr, R′=iPr ( 3 b , 84 %) or Ph ( 3 c , 45 %). Selective N‐methylation of the imidazole imine moiety in 3 b by MeOTf (OTf=OSO₂CF₃) gave the corresponding imidazoliophosphine [(^iPrPIMIOCOP^iPr)NiBr][OTf], 4 b , in 89 % yield (^iPrPIMIOCOP^iPr=κ^P,κ^C,κ^P‐{2‐(iPr₂PO),6‐(iPr₂PC₄H₅N₂)C₆H₃}). Treating 4 b with NaOEt led to the NHC derivative [(NHCCOP^iPr)NiBr], 5 b , in 47 % yield (NHCCOP^iPr=κ^P,κ^C,κ^C‐{2‐(iPr₂PO),6‐(C₄H₅N₂)C₆H₃)}). The bromo derivatives 3–5 were then treated with AgOTf in acetonitrile to give the corresponding cationic species [(^RPIMCOP^R)Ni(MeCN)][OTf] [R=Ph, 6 a (89 %) or iPr, 6 b (90 %)], [(^RPIMIOCOP^R)Ni(MeCN)][OTf]₂ [R=Ph, 7 a (79 %) or iPr, 7 b (88 %)], and [(NHCCOP^R)Ni(MeCN)][OTf] [R=Ph, 8 a (85 %) or iPr, 8 b (84 %)]. All new complexes have been characterized by NMR and IR spectroscopy, whereas 3 b , 3 c , 5 b , 6 b , and 8 a were also subjected to X‐ray diffraction studies. The acetonitrile adducts 6 – 8 were further studied by using various theoretical analysis tools. In the presence of excess nitrile and amine, the cationic acetonitrile adducts 6 – 8 catalyze hydroamination of nitriles to give unsymmetrical amidines with catalytic turnover numbers of up to 95.     

An Inverted‐Sandwich Diuranium μ‐η5:η5‐Cyclo‐P5 Complex Supported by U‐P5 δ‐Bonding

Reaction of [U(Tren^TIPS)] [ 1 , Tren^TIPS=N(CH₂CH₂NSiiPr₃)₃] with 0.25 equivalents of P₄ reproducibly affords the unprecedented actinide inverted sandwich cyclo‐P₅ complex [{U(Tren^TIPS)}₂(μ‐η⁵:η⁵‐cyclo‐P₅)] ( 2 ). All prior examples of cyclo‐P₅ are stabilized by d‐block metals, so 2 shows that cyclo‐P₅ does not require d‐block ions to be prepared. Although cyclo‐P₅ is isolobal to cyclopentadienyl, which usually bonds to metals via σ‐ and π‐interactions with minimal δ‐bonding, theoretical calculations suggest the principal bonding in the U(P₅)U unit is polarized δ‐bonding. Surprisingly, the characterization data are overall consistent with charge transfer from uranium to the cyclo‐P₅ unit to give a cyclo‐P₅ charge state that approximates to a dianionic formulation. This is ascribed to the larger size and superior acceptor character of cyclo‐P₅ compared to cyclopentadienyl, the strongly reducing nature of uranium(III), and the availability of uranium δ‐symmetry 5f orbitals.     

Synthesis,Structure, and Reactivity of RuII Complexes with Trimethylsilylethinylamidinate Ligands

The mononuclear amidinate complexes [(η⁶‐cymene)‐RuCl( 1a )] ( 2 ) and [(η⁶‐C₆H₆)RuCl( 1b )] ( 3 ), with the trimethylsilyl‐ethinylamidinate ligands [Me₃SiC≡CC(N‐c‐C₆H₁₁)₂]^– ( 1a^– ) and[Me₃SiC≡CC(N‐i‐C₃H₇)₂]^– ( 1b^– ) were synthesized in high yields by salt metathesis. In addition, the related phosphane complexes[(η⁵‐C₅H₅)Ru(PPh₃)( 1b )] ( 4a ) [(η⁵‐C₅Me₅)Ru(PPh₃)( 1b )] ( 4b ), and [(η⁶‐C₆H₆)Ru(PPh₃)( 1b )](BF₄) ( 5 ‐BF₄) were prepared by ligand exchange reactions. Investigations on the removal of the trimethyl‐silyl group using [Bu₄N]F resulted in the isolation of [(η⁶‐C₆H₆)Ru(PPh₃){(N‐i‐C₃H₇)₂CC≡CH}](BF₄) ( 6 ‐BF₄) bearing a terminal alkynyl hydrogen atom, while 2 and 3 revealed to yield intricate reaction mixtures. Compounds 1a / b to 6 ‐BF₄ were characterized by multinuclear NMR (¹H, ¹³C, ³¹P) and IR spectroscopy and elemental analyses, including X‐ray diffraction analysis of 1b , 2 , and 3 .     

Stabilization of a Silaaldehyde by its η2 Coordination to Tungsten

Treatment of pyridine‐stabilized silylene complexes [(η⁵‐C₅Me₄R)(CO)₂(H)W?SiH(py)(Tsi)] (R=Me, Et; py=pyridine; Tsi=C(SiMe₃)₃) with an N‐heterocyclic carbene ^MeIⁱPr (1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) caused deprotonation to afford anionic silylene complexes [(η⁵‐C₅Me₄R)(CO)₂W?SiH(Tsi)][H^MeIⁱPr] (R=Me ( 1‐Me ); R=Et ( 1‐Et )). Subsequent oxidation of 1‐Me and 1‐Et with pyridine‐N‐oxide (1 equiv) gave anionic η²‐silaaldehydetungsten complexes [(η⁵‐C₅Me₄R)(CO)₂W{η²‐O?SiH(Tsi)}][H^MeIⁱPr] (R=Me ( 2‐Me ); R=Et ( 2‐Et )). The formation of an unprecedented W‐Si‐O three‐membered ring was confirmed by X‐ray crystal structure analysis.     

2, 4‐Dimethylpenta‐1, 3‐dien‐ und 2, 4‐Dimethylpentadienyl‐Komplexe des Rhodiums und Iridiums

2, 4‐Dimethylpenta‐1, 3‐diene and 2, 4‐Dimethylpentadienyl Complexes of Rhodium and Iridium The complexes [(η⁴‐C₇H₁₂)RhCl]₂ ( 1 ) (C₇H₁₂ = 2, 4‐dimethylpenta‐1, 3‐diene) and [(η⁴‐C₇H₁₂)₂IrCl] ( 2 ) were obtained by interaction of C₇H₁₂ with [(η²‐C₂H₄)₂RhCl]₂ and [(η²‐cyclooctene)₂IrCl]₂, respectively. The reaction of 1 or 2 with CpTl (Cp = η⁵‐C₅H₅) yields the compounds [CpM(η⁴‐C₇H₁₂)] ( 3a : M = Rh; 3b : M = Ir). The hydride abstraction at the pentadiene ligand of 3a , b with Ph₃CBF₄ proceeds differently depending on the solvent. In acetone or THF the “half‐open” metallocenium complexes [CpM(η⁵‐C₇H₁₁)]BF₄ ( 4a : M = Rh; 4b : M = Ir) are obtained exclusively. In dichloromethane mixtures are produced which additionally contain the species [(η⁵‐C₇H₁₁)M(η⁵‐C₅H₄CPh₃)]BF₄ ( 5a : M = Rh; 5b : M = Ir) formed by electrophilic substitution at the Cp ring, as well as the η³‐2, 4‐dimethylpentenyl compound [(η³‐C₇H₁₃)Rh{η⁵‐C₅H₃(CPh₃)₂}]BF₄ ( 6 ). By interaction of 2, 4‐dimethylpentadienyl potassium with 1 or 2 the complexes [(η⁴‐C₇H₁₂)M(η⁵‐C₇H₁₁)] ( 7a : M = Rh; 7b : M = Ir) are generated which show dynamic behaviour in solution; however, attempts to synthesize the “open” metallocenium cations [(η⁵‐C₇H₁₁)₂M]⁺ by hydride abstraction from 7a , b failed. The new compounds were characterized by elemental analysis and spectroscopically, 4b and 5a also by X‐ray structure analysis.     

Diimido‐, Imido(oxo)‐, Dioxo‐ und Imido(alkyliden)‐Halbsandwich‐Verbindungen über selektive Hydrolyse und α—H‐Abstraktion an Organylkomplexen des sechswertigen Molybdäns und Wolframs

Diimido, Imido Oxo, Dioxo, and Imido Alkylidene Halfsandwich Compounds via Selective Hydrolysis and α—H Abstraction in Molybdenum(VI) and Tungsten(VI) Organyl Complexes Organometal imides [(η⁵‐C₅R₅)M(NR′)₂Ph] (M = Mo, W, R = H, Me, R′ = Mes, tBu) 4 — 8 can be prepared by reaction of halfsandwich complexes [(η⁵‐C₅R₅)M(NR′)₂Cl] with phenyl lithium in good yields. Starting from phenyl complexes 4 — 8 as well as from previously described methyl compounds [(η⁵‐C₅Me₅)M(NtBu)₂Me] (M = Mo, W), reactions with aqueous HCl lead to imido(oxo) methyl and phenyl complexes [(η⁵‐C₅Me₅)M(NtBu)(O)(R)] M = Mo, R = Me ( 9 ), Ph ( 10 ); M = W, R = Ph ( 11 ) and dioxo complexes [(η⁵‐C₅Me₅)M(O)₂(CH₃)] M = Mo ( 12 ), M = W ( 13 ). Hydrolysis of organometal imides with conservation of M‐C σ and π bonds is in fact an attractive synthetic alternative for the synthesis of organometal oxides with respect to known strategies based on the oxidative decarbonylation of low valent alkyl CO and NO complexes. In a similar manner, protolysis of [(η⁵‐C₅H₅)W(NtBu)₂(CH₃)] and [(η⁵‐C₅Me₅)Mo(NtBu)₂(CH₃)] by HCl gas leads to [(η⁵‐C₅H₅)W(NtBu)Cl₂(CH₃)] 14 und [(η⁵‐C₅Me₅)Mo(NtBu)Cl₂(CH₃)] 15 with conservation of the M‐C bonds. The inert character of the relatively non‐polar M‐C σ bonds with respect to protolysis offers a strategy for the synthesis of methyl chloro complexes not accessible by partial methylation of [(η⁵‐C₅R₅)M(NR′)Cl₃] with MeLi. As pure substances only trimethyl compounds [(η⁵‐C₅R₅)M(NtBu)(CH₃)₃] 16 ‐ 18 , M = Mo, W, R = H, Me, are isolated. Imido(benzylidene) complexes [(η⁵‐C₅Me₅)M(NtBu)(CHPh)(CH₂Ph)] M = Mo ( 19 ), W ( 20 ) are generated by alkylation of [(η⁵‐C₅Me₅)M(NtBu)Cl₃] with PhCH₂MgCl via α‐H abstraction. Based on nmr data a trend of decreasing donor capability of the ligands [NtBu]^2— > [O]^2— > [CHR]^2— ? 2 [CH₃]^— > 2 [Cl]^— emerges.     

Plumbocenes with sec- und tert-Alkyl Substituents

[(C₅H₂tBu₃-1,2,4)₂Pb] ( 1 ), [(C₅HiPr₄)₂Pb] ( 2 ), and [(C₅iPr₅)₂Pb] ( 3 ) have been obtained from PbCl₂ and Li(C₅H₂tBu₃-1,2,4), Na(C₅HiPr₄) and Na(C₅iPr₅), respectively. 3 exists as a 1 : 1 mixture of meso- 3 and rac- 3 which interconvert at elevated temperature via one-at-a-time rotation of isopropyl groups with ΔG^# = 73.0 ± 1.5/73.7 ± 1.5 kJ/mol at 348 K. 3 is slightly bent in the solid state with an angle of 170(1)° between the ring normals.     

On the Stability of a POCsp3OP‐Type Pincer Ligand in Nickel(II) Complexes

We describe the results of a study on the stabilities of pincer‐type nickel complexes relevant to catalytic hydroalkoxylation and hydroamination of olefins, C? C and C? X couplings, and fluorination of alkyl halides. Complexes [(POC_sp3OP)NiX] are stable for X=OSiMe₃, OMes (Mes=1,3,5‐Me₃C₆H₂), NPh₂, and CC? H, whereas the O(tBu) and N(SiMe₃)₂ derivatives decompose readily. The phenylacetylide derivative transforms gradually into the zero‐valent species cis‐[{κ^P,κ^C,κ^C′‐(iPr₂POCH₂CHCH₂)}Ni{η²,κ^C,κ^C′‐(iPr₂P(O)CCPh)}]. Likewise, attempts to prepare [(POC_sp3OP)NiF] gave instead the zwitterionic trinuclear species [{(η³‐allyl)Ni}₂‐{μ,κ^P,κ^O‐(iPr₂PO)₄Ni}]. Characterization of these two complexes provides concrete examples of decomposition processes that can dismantle POC_sp3OP‐type pincer ligands by facile C? O bond rupture. These results serve as a cautionary tale for the inherent structural fragility of pincer systems bearing phosphinite donor moieties, and provide guidelines on how to design more robust analogues.     

Syntheses and Characterization of Samarium and Erbium Borohydrido Complexes Supported by N‐Aryliminopyrrole Ligand

Reaction of potassium salt of N‐aryliminopyrrole ligand [2‐(2, 6‐iPr₂C₆H₃N=CH)–C₄H₃NK] ( 1 ) with samarium tris‐boro‐hydride [Sm(BH₄)₃(THF)₃] gave a samarium ate complex [η²‐{2‐(2, 6‐iPr₂C₆H₃N=CH)–C₄H₃N}₃Sm(η¹‐BH₄){K(THF)₆] ( 2 ); whereas similar treatment with erbium borohydride [Er(BH₄)₃(THF)₃] afforded the mono(iminopyrrolyl) complex [η²‐{2‐(2, 6‐iPr₂C₆H₃N=CH)–C₄H₃N}Er(η³‐BH₄)₂(THF)₂] ( 3 ). In the solid‐state structures, the samarium complex 2 shows a rarely observed η¹ and the erbium complex 3 shows a usual η³ coordination mode of the borohydrido ligand.     

Heterobimetallische phosphanido-verbrückte Zweikern-Komplexe - Synthese von cis-rac-[(η-C5H4R)2Zr{μ-PH(2,4,6−iPr3C6H2)}2M(CO)4] (RMe,MCr,Mo; RH,MMo)

Heterobimetallic Phosphanido-bridged Dinuclear Complexes - Syntheses of cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] (R?Me, M?Cr, Mo; R?H, M?Mo) The zirconocene bisphosphanido complexes [(η-C₅H₄R)₂Zr{PH(2,4,6-ⁱPr₃C₆H₂)}₂] (R?Me, H) react with [(NBD)M(CO)₄] (NBD?norbornadiene, M?Cr, Mo) to give only one diastereomer of the phosphanido-bridged heterobimetallic dinuclear complexes cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] [R?Me, M?Cr ( 1 ), Mo ( 2 ); R?H, M?Mo ( 3 )]. However, no reaction was observed between [(η-C₅H₅)₂Zr{PH(2,4,6-^tBu₃ C₆H₂)}₂] and [Pt(PPh₃)₄]. 1—3 were characterised spectroscopically. For 1—3 , the presence of the racemic isomer was shown by NMR spectroscopy. No reaction was observed at room temperature for 3 and CS₂, (NO)BF₄, Me₃NO or PH(2,4,6-Me₃C₆H₂)₂. With Et₂AlH or PhC?CH decomposition of 3 was observed.     

The Synthesis,Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

The coordination chemistry of the 1,2‐BN‐cyclohexanes 2,2‐R₂‐1,2‐B,N‐C₄H₁₀ (R₂=HH, MeH, Me₂) with Ir and Rh metal fragments has been studied. This led to the solution (NMR spectroscopy) and solid‐state (X‐ray diffraction) characterization of [Ir(PCy₃)₂(H)₂(η²η²‐H₂BNR₂C₄H₈)][BAr^F₄] (NR₂=NH₂, NMeH) and [Rh(iPr₂PCH₂CH₂CH₂PiPr₂)(η²η²‐H₂BNR₂C₄H₈)][BAr^F₄] (NR₂=NH₂, NMeH, NMe₂). For NR₂=NH₂ subsequent metal‐promoted, dehydrocoupling shows the eventual formation of the cyclic tricyclic borazine [BNC₄H₈]₃, via amino‐borane and, tentatively characterized using DFT/GIAO chemical shift calculations, cycloborazane intermediates. For NR₂=NMeH the final product is the cyclic amino‐borane HBNMeC₄H₈. The mechanism of dehydrogenation of 2,2‐H,Me‐1,2‐B,N‐C₄H₁₀ using the {Rh(iPr₂PCH₂CH₂CH₂PiPr₂)}⁺ catalyst has been probed. Catalytic experiments indicate the rapid formation of a dimeric species, [Rh₂(iPr₂PCH₂CH₂CH₂PiPr₂)₂H₅][BAr^F₄]. Using the initial rate method starting from this dimer, a first‐order relationship to [amine‐borane], but half‐order to [Rh] is established, which is suggested to be due to a rapid dimer–monomer equilibrium operating.     

Unexpected Coordination Modes of the Tris(imidazolyl)phosphane Oxide Ligand 4‐TIPOiPr in the Chloro Complexes of Zinc,Cobalt and Nickel

The coordination chemistry of the water soluble phosphane oxide ligand tris[2‐isopropylimidazol‐4(5)‐yl]phosphane oxide, 4‐TIPO^iPr, has been explored. A variety of 3d‐metal halide complexes have been prepared and the crystal structures of the solvates [(4‐TIPO^iPr)ZnCl₂]·MeOH·¹/₂dioxane ( 1 ·MeOH·¹/₂dioxane), [(4‐TIPO^iPr)CoCl₂]·H₂O·2dioxane ( 2 ·H₂O·2dioxane) and [(4‐TIPO^iPr)₂Ni(MeOH)₂]Cl₂·2MeOH ( 3 ·2MeOH) have been determined. All three structures show unprecedented coordination modes of the 4‐TIPO^iPr ligand. Both zinc and cobalt complexes are coordinated in a bidentate κ²N fashion, whereas the nickel atom is coordinated by two ligands in a κN,O mode using one imidazolyl substituent and the P=O oxygen atom.     

Regioselective Insertion of Aluminum(I) in the cyclo‐P5 Ring of Pentaphosphaferrocene

A route to directly access mixed Al–Fe polyphosphide complexes was developed. The reactivity of pentaphosphaferrocene, [Cp*Fe(η⁵‐P₅)] (Cp*=C₅Me₅), with two different low‐valent aluminum compounds was investigated. The steric and electronic environment around the [Al^I] centre are found to be crucial for the formation of the resulting Al–Fe polyphosphides. Reaction with the sterically demanding [Dipp‐BDIAl^I] (Dipp‐BDI={[2,6‐ⁱPr₂C₆H₃NCMe]₂CH}^?) resulted in the first Al‐based neutral triple‐decker type polyphosphide complex. For [(Cp*Al^I)₄], an unprecedented regioselective insertion of three [Cp*Al^III]²⁺ moieties into two adjacent P?P bonds of the cyclo‐P₅ ring of [Cp*Fe(η⁵‐P₅)] was observed. The regioselectivity of the insertion reaction could be rationalized by isolating an analogue of the reaction intermediate stabilized by a strong σ‐donor carbene.     

Syntheses and Molecular Structure of Dinuclear Transition Metal Complexes Bridged by Dipyridylamine Derivative Ligands

Stable dinuclear transition metal complexes,[(η⁶‐C₆H₆)₂Ru₂(L1)Cl₂]²⁺ ( 1 ), [(η⁶‐p‐iPrC₆H₄Me)₂Ru₂(L1)Cl₂]²⁺ ( 2 ), [(η⁶‐C₆Me₆)₂Ru₂(L1)Cl₂]²⁺ ( 3 ), [(η⁶‐C₆H₆)₂Ru₂(L2)Cl₂]²⁺ ( 4 ),[(η⁶‐p‐iPrC₆H₄Me)₂Ru₂(L2)Cl₂]²⁺ ( 5 ), [(η⁶‐C₆Me₆)₂Ru₂(L2)Cl₂]²⁺ ( 6 ), [(η⁵‐C₅Me₅)₂Rh₂(L1)Cl₂]²⁺ ( 7 ), [(η⁵‐C₅Me₅)₂Ir₂(L1)Cl₂]²⁺ ( 8 ),[(η⁵‐C₅Me₅)₂Rh₂(L2)Cl₂]²⁺ ( 9 ), and [(η⁵‐C₅Me₅)₂Rh₂(L2)Cl₂]²⁺ ( 10 ), with the bis‐bidentate ligands 1,3‐bis(di‐2‐pyridylaminomethyl)benzene (L1) and 1,4‐bis(di‐2‐pyridylaminomethyl)benzene (L2), which contain two chelating dipyridylamine units connected by an aromatic spacer, were synthesized. The cationic dinuclear complexes were isolated as their hexafluorophosphate salts and characterized by using a combination of NMR, IR, and UV/Vis spectroscopic methods and mass spectrometry. The solid‐state structure of complex 8 as a representative was determined by X‐ray structure analysis.     

Isolation of Elusive HAsAsH in a Crystalline Diuranium(IV) Complex

The HAsAsH molecule has hitherto only been proposed tentatively as a short‐lived species generated in electrochemical or microwave‐plasma experiments. After two centuries of inconclusive or disproven claims of HAsAsH formation in the condensed phase, we report the isolation and structural authentication of HAsAsH in the diuranium(IV) complex [{U(Tren^TIPS)}₂(μ‐η²:η²‐As₂H₂)] ( 3 , Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃; Prⁱ=CH(CH₃)₂). Complex 3 was prepared by deprotonation and oxidative homocoupling of an arsenide precursor. Characterization and computational data are consistent with back‐bonding‐type interactions from uranium to the HAsAsH π*‐orbital. This experimentally confirms the theoretically predicted excellent π‐acceptor character of HAsAsH, and is tantamount to full reduction to the diarsane‐1,2‐diide form.