Reaction of the Pincer‐type Ligand {2, 6‐[P(O)(OEt)2]2‐4‐tert‐Bu‐C6H2}— with [Ph3C]+[PF6]—. Unprecedented Rearrangement and Carbon‐Carbon Bond Formation

The reaction of the organolithium derivative {2, 6‐[P(O)(OEt)₂]₂‐4‐tert‐Bu‐C₆H₂}Li ( 1 ‐Li) with [Ph₃C]⁺[PF₆]^— gave the substituted biphenyl derivative 4‐[(C₆H₅)₂CH]‐4′‐[tert‐Bu]‐2′, 6′‐[P(O)(OEt)₂]₂‐1, 1′‐biphenyl ( 5 ) which was characterized by ¹H, ¹³C and ³¹P NMR spectroscopy and single crystal X‐ray analysis. Ab initio MO‐calculations reveal the intramolecular O···C distances in 5 of 2.952(4) and 2.988(5)Å being shorter than the sum of the van der Waals radii of oxygen and carbon to be the result of crystal packing effects. Also reported are the synthesis and structure of the bromine‐substituted derivative {2, 6‐[P(O)(OEt)₂]₂‐4‐tert‐Bu]C₆H₂}Br ( 9 ) and the structure of the protonated ligand 5‐tert‐Bu‐1, 3‐[P(O)(OEt)₂]₂C₆H₃ ( 1 ‐H). The structures of 1 ‐H, 5 , and 9 are compared with those of related metal‐substituted derivatives.     

Insights into the Intramolecular Donor Stabilisation of Organostannylene Palladium and Platinum Complexes: Syntheses,Structures and DFT Calculations

The syntheses of the transition metal complexes cis‐[(4‐tBu‐2,6‐{P(O)(OiPr)₂}₂C₆H₂SnCl)₂MX₂] ( 1 , M=Pd, X=Cl; 2 , M=Pd, X=Br; 3 , M=Pd, X=I; 4 , M=Pt, X=Cl), cis‐[{2,6‐(Me₂NCH₂)₂C₆H₃SnCl}₂MX₂] ( 5 , M=Pd, X=I; 6 , M=Pt, X=Cl), trans‐[{2,6‐(Me₂NCH₂)₂C₆H₃SnI}₂PtI₂] ( 7 ) and trans‐[(4‐tBu‐2,6‐{P(O)(OiPr)₂}₂ C₆H₂SnCl)PdI₂]₂ ( 8 ) are reported. Also reported is the serendipitous formation of the unprecedented complexes trans‐[(4‐tBu‐2,6‐{P(O)(OiPr)₂}₂C₆H₂SnCl)₂ Pt(SnCl₃)₂] ( 10 ) and [(4‐tBu‐2,6‐{P(O) (OiPr)₂}₂C₆H₂SnCl)₃Pt(SnCl₃)₂] ( 11 ). The compounds were characterised by elemental analyses, ¹H, ¹³C, ³¹P, ¹¹⁹Sn and ¹⁹⁵Pt NMR spectroscopy, single‐crystal X‐ray diffraction analysis, UV/Vis spectroscopy and, in the cases of compounds 1 , 3 and 4 , also by Mössbauer spectroscopy. All the compounds show the tin atoms in a distorted trigonal‐bipyramidal environment. The Mössbauer spectra suggest the tin atoms to be present in the oxidation state III. The kinetic lability of the complexes was studied by redistribution reactions between compounds 1 and 3 as well as between 1 and cis‐[{2,6‐(Me₂NCH₂)₂C₆H₃SnCl}₂PdCl₂]. DFT calculations provided insights into both the bonding situation of the compounds and the energy difference between the cis and trans isomers. The latter is influenced by the donor strength of the pincer‐type ligands.     

Vanadium(V) Oxo and Imido Calix[8]arene Complexes: Synthesis,Structural Studies,and Ethylene Homo/Copolymerisation Capability

Interaction of p‐tert‐butylcalix[8]areneH₈ (L⁸H₈) with [NaVO(OtBu)₄] (formed in situ from VOCl₃) afforded the complex [Na(NCMe)₅][(VO)₂L⁸H]?4 MeCN ( 1 ?4 MeCN). Increasing [NaVO(OtBu)₄] to 4 equiv led to [Na(NCMe)₆]₂[(Na(VO)₄L⁸)(Na(NCMe))₃]₂?10 MeCN ( 2 ?10 MeCN). With adventitious oxygen, reaction of 4 equiv of [VO(OtBu)₃] with L⁸H₈ afforded the alkali‐metal‐free complex [(VO)₄L⁸(μ³‐O)₂] ( 3 ); solvates 3 ?3 MeCN and 3 ?3 CH₂Cl₂ were isolated. For the lithium analogue, the order of addition had to be reversed such that lithium tert‐butoxide was added to L⁸H₈ and then treated with 2 equiv of VOCl₃; crystallisation afforded [(VO₂)₂Li₆[L⁸](thf)₂(OtBu)₂(Et₂O)₂]?Et₂O ( 4 ?Et₂O). Upon extraction into acetonitrile, [Li(NCMe)₄][(VO)₂L⁸H]?8 MeCN ( 5 ?8 MeCN) was formed. Use of the imido precursors [V(NtBu)(OtBu)₃] and [V(Np‐tolyl)(OtBu)₃] and L⁸H₈, afforded [tBuNH₃][{V(p‐tolylN)}₂L⁸H]?3 1/2 MeCN ( 6 ?3 1/2 MeCN). The molecular structures of 1 to 6 are reported. Complexes 1 , 3 , and 4 were screened as precatalysts for the polymerisation of ethylene in the presence of cocatalysts at various temperatures and for the copolymerisation of ethylene with propylene. Activities as high as 136 000 g (mmol(V) h)^?1 were sometimes achieved; higher molecular weight polymers could be obtained versus the benchmark [VO(OEt)Cl₂]. For copolymerisation, incorporation of propylene was 7.1–10.9 mol % (compare 10 mol % for [VO(OEt)Cl₂]), although catalytic activities were lower than [VO(OEt)Cl₂].     

Synthesis of New Phosphonium Ylides Containing Thiophene and Furan Rings and Study of Their Reaction with Mercury(II) Halides: Spectral and Structural Characterization

Reactions of phosphonium ylides (4‐MeC₆H₄)₃PCHC(?O)(2‐C₄H₃S) (tptpy), Ph₃PCHC(?O)(2‐C₄H₃O) (fppy), and (4‐MeC₆H₄)₃PCHC(?O)(4‐BrC₆H₄) (bbtppy) with HgX₂ (X=Cl, Br, and I) in equimolar ratios in MeOH as solvent leads to the binuclear products 1 – 3 (Scheme 1). The bridge‐splitting reaction of the binuclear complex [{HgI₂(bbtppy)}₂] ( 3c ) by DMSO yields the mononuclear complex [HgI₂?(bbtppy) (DMSO)] ( 3d ) (Scheme 2). This bridge‐splitting reaction can also be a method for the synthesis of mononuclear products. C‐Coordination of the ylide and O‐coordination of DMSO are demonstrated by a single‐crystal X‐ray‐analysis of the mononuclear complex 3d . Characterization of the obtained compounds was also performed by means of elemental analysis and IR and ¹H‐, ³¹P‐, and ¹³C‐NMR spectroscopy. A theoretical study of some Hg^II complexes with phosphonium ylides is also reported.     

From Dibismuthenes to Three‐ and Two‐Coordinated Bismuthinidenes by Fine Ligand Tuning: Evidence for Aromatic BiC3N Rings through a Combined Experimental and Theoretical Study

The reduction of N,C,N‐chelated bismuth chlorides [C₆H₃‐2,6‐(CH?NR)₂]BiCl₂ [where R=tBu ( 1 ), 2′,6′‐Me₂C₆H₃ ( 2 ), or 4′‐Me₂NC₆H₄ ( 3 )] or N,C‐chelated analogues [C₆H₂‐2‐(CH?N‐2′,6′‐iPr₂C₆H₃)‐4,6‐(tBu)₂]BiCl₂ ( 4 ) and [C₆H₂‐2‐(CH₂NEt₂)‐4,6‐(tBu)₂]BiCl₂ ( 5 ) is reported. Reduction of compounds 1 – 3 gave monomeric N,C,N‐chelated bismuthinidenes [C₆H₃‐2,6‐(CH?NR)₂]Bi [where R=tBu ( 6 ), 2′,6′‐Me₂C₆H₃ ( 7 ) or 4′‐Me₂NC₆H₄ ( 8 )]. Similarly, the reduction of 4 led to the isolation of the compound [C₆H₂‐2‐(CH?N‐2′,6′‐iPr₂C₆H₃)‐4,6‐(tBu)₂]Bi ( 9 ) as an unprecedented two‐coordinated bismuthinidene that has been structurally characterized. In contrast, the dibismuthene {[C₆H₂‐2‐(CH₂NEt₂)‐4,6‐(tBu)₂]Bi}₂ ( 10 ) was obtained by the reduction of 5 . Compounds 6 – 10 were characterized by using ¹H and ¹³C NMR spectroscopy and their structures, except for 7 , were determined with the help of single‐crystal X‐ray diffraction analysis. It is clear that the structure of the reduced products (bismuthinidene versus dibismuthene) is ligand‐dependent and particularly influenced by the strength of the N→Bi intramolecular interaction(s). Therefore, a theoretical survey describing the bonding situation in the studied compounds and related bismuth(I) systems is included. Importantly, we found that the C₃NBi chelating ring in the two‐coordinated bismuthinidene 9 exhibits significant aromatic character by delocalization of the bismuth lone pair.     

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.     

Synthesis and Structures of New Oxidation/ Cycloaddition Products of λ3‐Cyclodiphosphazanes

Reaction of the cyclodiphosphazane [(OC₄H₈N)P(μ‐N‐t‐Bu)₂P(HN‐t‐Bu)] ( 1 ) with an equimolar quantity of diisopropyl azodicarboxylate afforded the phosphinimine product [(OC₄H₈N)P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂ ‐i‐Pr)NHCO₂‐i‐Pr] ( 6 ) having a P^III‐N‐P^V skeleton. Similar products [(t‐BuNH)P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂Et)NHCO₂Et] ( 7 ) and [(CO₂‐i‐Pr)HNN(CO₂‐i‐Pr)](t‐BuN=P(μ‐N‐t‐Bu)₂POCH₂CMe₂CH₂O[P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂‐i‐Pr)NH(CO₂‐i‐Pr)] ( 8 ) were spectroscopically characterized in the reaction of [(t‐BuNH)P‐N‐t‐Bu]₂ ( 2 ) and [(t‐BuNH)P(μ‐N‐t‐Bu)₂POCH₂CMe₂CH₂OP(μ‐N‐t‐Bu)₂P(NH‐t‐Bu)] ( 3 ) with diethyl‐ and diisopropyl azodicarboxylate, respectively. By contrast, the reaction of [(μ‐t‐BuN)P]₂[O‐6‐t‐Bu‐4‐Me‐C₆H₂]₂CH₂ ( 4 ) and [(C₅H₁₀N)P‐μ‐N‐t‐Bu]₂ ( 5 ) with diisopropyl azodicarboxylate afforded the mono‐ and bis‐oxidized compounds [(O)P(μ‐N‐t‐Bu)₂P][O‐6‐t‐Bu‐4‐Me‐C₆H₂]₂CH₂ ( 9 ) and [(C₅H₁₀N)(O)P‐μ‐N‐t‐Bu]₂ ( 10 ), respectively. Oxidative addition of o‐chloranil to 7 and its DIAD analogue [(t‐BuNH)P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂‐i‐Pr)NHCO₂‐i‐Pr] ( 11 ) afforded [(C₆Cl₄‐1, 2‐O₂)(t‐BuNH)P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂R)NHCO₂R] [R = Et ( 12 ) and i‐Pr ( 13 )] containing tetra‐ and pentacoordinate P^V atoms in the cyclodiphosphazane ring. The structures of 6 , 9 , 12 and 13 have been confirmed by X‐ray structure determination. For comparison, the X‐ray structure of the double cycloaddition product [(C₆Cl₄‐1, 2‐O₂)(t‐BuNH)PN‐t‐Bu]₂ ( 14 ), obtained from the reaction of 2 with two mole equivalents of o‐chloranil is also reported.     

Chromium complexes bearing disubstituted organophosphate ligands and their use in ethylene polymerization

The crystal structures of three unusual chromium organophosphate complexes have been determined, namely, bis(μ‐butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl hydrogen phosphato‐κO:κO′)di‐μ‐hydroxido‐bis[(butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl hydrogen phosphato‐κO)(butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl phosphato‐κO)chromium](Cr—Cr) heptane disolvate or {Cr₂(μ₂‐OH)₂[μ₂‐PO₂(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO:κO′]₂[PO₂(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO]₂[HOPO(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO]₂}·2C₇H₁₆, [Cr₂(C₁₉H₃₂O₄P)₄(C₁₉H₃₃O₄P)₂(OH)₂]·2C₇H₁₆, denoted ( 1 )·2(heptane), [μ‐bis(2,6‐diisopropylphenyl) phosphato‐1κO:2κO′]bis[bis(2,6‐diisopropylphenyl) phosphato]‐1κO,2κO‐chlorido‐2κCl‐triethanol‐1κ²O,2κO‐di‐μ‐ethanolato‐1κ²O:2κ²O‐dichromium(Cr—Cr) ethanol monosolvate or {Cr₂(μ₂‐OEt)₂[μ₂‐PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO:κO′][PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂Cl(EtOH)₃}·EtOH, [Cr₂(C₂H₅O)₂(C₂₄H₃₄O₄P)₃Cl(C₂H₆O)₃]·C₂H₆O, denoted ( 2 )·EtOH, and di‐μ‐ethanolato‐1κ²O:2κ²O‐bis{[bis(2,6‐diisopropylphenyl) hydrogen phosphato‐κO][bis(2,6‐diisopropylphenyl) phosphato‐κO]chlorido(ethanol‐κO)chromium}(Cr—Cr) benzene disolvate or {Cr₂(μ₂‐OEt)₂[PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂[HOPO(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂Cl₂(EtOH)₂}·2C₆H₆, [Cr₂(C₂H₅O)₂(C₂₄H₃₄O₄P)₂(C₂₄H₃₅O₄P)₂Cl₂(C₂H₆O)₂]·2C₆H₆, denoted ( 3 )·2C₆H₆. Complexes ( 1 )–( 3 ) have been synthesized by an exchange reaction between the in‐situ‐generated corresponding lithium or potassium disubstituted phosphates with CrCl₃(H₂O)₆ in ethanol. The subsequent crystallization of ( 1 ) from heptane, ( 2 ) from ethanol and ( 3 ) from an ethanol/benzene mixture allowed us to obtain crystals of ( 1 )·2(heptane), ( 2 )·EtOH and ( 3 )·2C₆H₆, whose structures have the monoclinic P2₁, orthorhombic P2₁2₁2₁ and triclinic P space groups, respectively. All three complexes have binuclear cores with a single Cr—Cr bond, i.e. Cr₂O₆P₂ in ( 1 ), Cr₂PO₄ in ( 2 ) and Cr₂O₂ in ( 3 ), where the Cr atoms are in distorted octahedral environments, formally having 16 ē per Cr atom. The complexes have bridging ligands μ₂‐OH in ( 1 ) or μ₂‐OEt in ( 2 ) and ( 3 ). The organophosphate ligands demonstrate terminal κO coordination modes in ( 1 )–( 3 ) and bridging μ₂‐κO:κO′ coordination modes in ( 1 ) and ( 2 ). All the complexes exhibit hydrogen bonding: two intramolecular O_phos…H—O_phos interactions in ( 1 ) and ( 3 ) form two {H[PO₂(OR)₂]₂} associates; two intramolecular Cl…H—O_Et hydrogen bonds additionally stabilize the Cr₂O₂ core in ( 3 ); two intramolecular O_phos…H—O_Et interactions and two O…H—O intermolecular hydrogen bonds with a noncoordinating ethanol molecule are observed in ( 2 )·EtOH. The presence of both basic ligands (OH^? or OEt^?) and acidic [H(phosphate)₂]^? associates at the same metal centres in ( 1 ) and ( 3 ) is rather unusual. Complexes may serve as precatalysts for ethylene polymerization under mild conditions, providing polyethylene with a small amount of short‐chain branching. The formation of a small amount of α‐olefins has been detected in this reaction.     

Phosphine (oxide)‐(thio) phenolate palladium complexes: Synthesis,characterization and (co)polymerization of norbornene

A series of palladium complexes ( 2a–2g ) ( 2a : [6‐^tBu‐2‐PPh₂‐C₆H₃O]PdMe(Py); 2b : [6‐C₆F₅–2‐PPh₂‐C₆H₃O]PdMe(Py); 2c : [6‐^tBu‐2‐PPh^tBu‐C₆H₃O]PdMe(Py); 2d : [2‐PPh^tBu‐C₆H₄O] PdMe(Py); 2e : [6‐SiMe₃–2‐PPh₂‐C₆H₃O]PdMe(Py); 2f : [2‐^tBu‐6‐(Ph₂P=O)‐C₆H₃O]PdMe(Py); 2g : [6‐SiMe₃–2‐(Ph₂P=O)‐C₆H₃S]PdMe(Py)) bearing phosphine (oxide)‐(thio) phenolate ligand have been efficiently synthesized and characterized. The solid‐state structures of complexes 2d , 2f and 2g have been further confirmed by single‐crystal X‐ray diffraction, which revealed a square‐planar geometry of palladium center. In the presence of B(C₆F₅)₃, these complexes can be used as catalysts to polymerize norbornene (NB) with relatively high yields, producing vinyl‐addition polymers. Interestingly, 2a /B(C₆F₅)₃ system catalyzed the polymerization of NB in living polymerization manner at high temperature (polydispersity index 1.07, M_n up to 1.5 × 10⁴). The co‐polymerization of NB and polar monomers was also studied using catalysts 2a and 2f . All the obtained co‐polymers could dissolve in common solvent.     

Synthesis and Characterization of β‐Diketiminate Aluminum Compounds and Their Use in the Ring‐Opening Polymerization of ε‐Caprolactone

Four aluminum alkyl compounds, [CH{(CH₃)CN‐2,4,6‐MeC₆H₂}₂AlMe₂] ( 1 ), [CH{(CH₃)CN‐2,4,6‐MeC₆H₂}₂AlEt₂] ( 2 ), [CH{(CH₃)CN‐2‐iPrC₆H₄}₂AlMe₂] ( 3 ), and [CH{(CH₃)CN‐2‐iPrC₆H₄}₂AlEt₂] ( 4 ), bearing β‐diketiminate ligands [CH{(Me)CN‐2,4,6‐MeC₆H₂}]₂ (L¹H) and [CH{(Me)CN‐2‐ⁱPrC₆H₄}]₂ (L²H) were obtained from the reactions of trimethylaluminum, triethylaluminum with the corresponding β‐diketiminate, respectively. All compounds were characterized by ¹H NMR and ¹³C NMR spectroscopy, single‐crystal X‐ray structural analysis, and elemental analysis. Compounds 1 – 4 were found to catalyze the ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) with good activity.     

Molybdenum(VI) Bis(imido) Complexes: From Frustrated Lewis Pairs to Weakly Coordinating Cations

Molybdenum(VI) bis(imido) complexes [Mo(NtBu)₂(L^R)₂] (R=H 1 a ; R=CF₃ 1 b ) combined with B(C₆F₅)₃ ( 1 a /B(C₆F₅)₃, 1 b /B(C₆F₅)₃) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H−H, Si−H and O−H bonds. Cleavage of H₂ and Et₃SiH affords ion pairs [Mo(NtBu)(NHtBu)(L^R)₂][HB(C₆F₅)₃] (R=H 2 a ; R=CF₃ 2 b ) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H₂O leads to [Mo(NtBu)(NHtBu)(L^R)₂][(HO)B(C₆F₅)₃] (R=H 3 a ; R=CF₃ 3 b ). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a . Mechanistic elucidation revealed insertion of the aldehyde into the B−H bond of [HB(C₆F₅)₃]⁻. We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(L^R)₂][{PhCH₂O}B(C₆F₅)₃] (R=H 4 a ; R=CF₃ 4 b ). Catalysis occurs at [HB(C₆F₅)₃]⁻ while [Mo(NtBu)(NHtBu)(L^R)₂]⁺ (R=H or CF₃) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC).     

Synthesis and Structure of (N,)C,N‐chelated Organoantimony(III) and Bismuth(III) Cations and Isolation of Their Adducts with Ag[CB11H12]

The treatment of N,C,N‐chelated antimony(III) and bismuth(III) chlorides [C₆H₃‐2,6‐(CH=NR)₂]MCl₂ [R = tBu and M = Sb ( 1 ) or Bi ( 2 ); R = Dmp and M = Sb ( 3 ) or Bi ( 4 )] (Dmp = 2,6‐Me₂C₆H₃) with one molar equivalent of Ag[CB₁₁H₁₂] led to a smooth formation of corresponding ionic pairs {[C₆H₃‐2,6‐(CH=NR)₂]MCl}⁺[CB₁₁H₁₂]^– [R = tBu and M = Sb ( 7 ) or Bi ( 8 ), R = Dmp and M = Sb ( 9 ) or Bi ( 10 )]. Similarly, the reaction of C,N‐chelated analogues [C₆H₂‐2‐(CH=NDip)‐4,6‐(tBu)₂]MCl₂ [M = Sb ( 5 ) or Bi ( 6 ), Dip = 2′,6′‐iPr₂C₆H₃] gave compounds {[C₆H₂‐2‐(CH=NDip)‐4,6‐(tBu)₂]MCl}⁺[CB₁₁H₁₂]^– [M = Sb ( 11 ) or Bi ( 12 )]. All compounds 7 – 12 were characterized with ¹H, ¹¹B and ¹³C{¹H} NMR spectroscopy, ESI‐mass spectrometry, IR spectroscopy, and molecular structures of 7 – 9 and 12 were determined by the help of single‐crystal X‐ray diffraction analysis. In contrast, all attempts to cleave also the second M–Cl bond in 7 – 12 using another molar equivalent Ag[CB₁₁H₁₂] remained unsuccessful. Nevertheless, the reaction between 7 (or 8 ) and Ag[CB₁₁H₁₂] produced unprecedented adducts of both reagents namely {[C₆H₃‐2,6‐(CH=NtBu)₂]SbCl}₂²⁺[Ag₂(CB₁₁H₁₂)₄]^2– ( 13 ) and {[C₆H₃‐2,6‐(CH=NtBu)₂]BiCl}⁺[Ag(CB₁₁H₁₂)₂]^– ( 14 ) in a reproducible manner. The molecular structures of these sparingly soluble compounds were determined by single‐crystal X‐ray diffraction analysis.     

1‐Azonia‐2‐boratanaphthalenes

The 1‐azonia‐2‐boratanaphthalenes (NH)(BX)C₈H₆ can be synthesized from 2‐aminostyrene and the dihaloboranes XBHal₂ ( 1 ‐ 4 : X = Cl, Br, iPr, tBu). Further derivatives (NH)(BX)C₈H₆ are obtained from 1 by replacing Cl by alkoxy or alkyl groups [ 5 ‐ 8 : X = OMe, OtBu, Me, (CH₂)₃NMe₂]. The hydrolysis of 1 gives a mixture of the bis(azoniaboratanaphthyl) oxide [(NH)BC₈H₆]₂O ( 9 ) and the hydroxy derivative (NH)[B(OH)]C₈H₆ ( 10 ). The diboryl oxide 9 crystallizes in the space group C2/c. The lithiation of 4 at the nitrogen atom gives [NLi(tmen)](BtBu)C₈H₆ ( 11 ), which upon reaction with the diborane(4) B₂Cl₂(NMe₂)₂ yields the 1, 2‐bis(azoniaboratanaphthyl)diborane B₂[N(BtBu)C₈H₆]₂(NMe₂)₂ ( 12 ). The 2‐chloro‐1‐methyl‐4‐phenyl derivative (NMe)(BCl)C₈H₅Ph ( 13 ) of the parent (NH)(BH)C₈H₆ can be synthesized from the aminoborane BCl₂(NMePh) and phenylethyne. Substitution of Cl in 13 gives the derivatives (NMe)(BX)C₈H₅Ph [ 14 ‐ 20 : X = N(SiMe₃)₂, Me, Et, iBu, tBu, CH₂SiMe₃, Ph] and the reaction of 13 with Li₂O affords the bis(azoniaboratanaphthyl) oxide [(NMe)BC₈H₅Ph]₂O ( 21 ). The reaction of 16 or 19 with [(MeCN)₃Cr(CO)₃] yields the complexes [{(NMe)(BX)C₈H₅Ph}Cr(CO)₃] ( 22 , 23 : X = Et, CH₂SiMe₃), in which the chromium atom is hexahapto bound to the homoarene part of 16 or 19 , respectively. The complex 23 crystallizes in the space group P2₁/c. Upon reaction of the phenols para‐C₆H₄R(OH) with the aryldichloroboranes ArBCl₂ and subsequent condensation of the products with phenylethyne, the 1‐oxonia‐2‐boratanaphthalenes O(BAr)C₈H₄RPh with R in position 6 and Ph in position 4 are formed ( 24 ‐ 26 : Ar = Ph, R = H, Me, OMe; 27 ‐ 29 : Ar = C₆F₅, R = H, Me, OMe). The azoniaboratanaphthalenes 1 ‐ 23 were characterized by NMR methods.     

Understanding the Subtleties of Frustrated Lewis Pair Activation of Carbonyl Compounds by N‐Heterocyclic Carbene/Alkyl Gallium Pairings

This study reports the use of the trisalkylgallium GaR₃ (R=CH₂SiMe₃), containing sterically demanding monosilyl groups, as an effective Lewis‐acid component for frustrated Lewis pair activation of carbonyl compounds, when combined with the bulky N‐heterocyclic carbene 1,3‐bis(tert‐butyl)imidazol‐2‐ylidene (ItBu) or 1,3‐bis(tert‐butyl)imidazolin‐2‐ylidene (SItBu). The reduction of aldehydes can be achieved by insertion into the C=O functionality at the C2 (so‐called normal) position of the carbene affording zwitterionic products [ItBuCH₂OGaR₃] ( 1 ) or [ItBuCH(p‐Br‐C₆H₄)OGaR₃] ( 2 ), or alternatively, at its abnormal (C4) site yielding [aItBuCH(p‐Br‐C₆H₄)OGaR₃] ( 3 ). As evidence of the cooperative behaviour of both components, ItBu and GaR₃, neither of them alone are able to activate any of the carbonyl‐containing substrates included in this study NMR spectroscopic studies of the new compounds point to complex equilibria involving the formation of kinetic and thermodynamic species as implicated through DFT calculations. Extension to ketones proved successful for electrophilic α,α,α‐trifluoroacetophenone, yielding [aItBuC(Ph)(CF₃)OGaR₃] ( 7 ). However, in the case of ketones and nitriles bearing acidic hydrogen atoms, C?H bond activation takes place preferentially, affording novel imidazolium gallate salts such as [{ItBuH}⁺{(p‐I‐C₆H₄)C(CH₂)OGaR₃}^?] ( 8 ) or [{ItBuH}⁺{Ph₂C=C=NGaR₃}^?] ( 12 ).     

Ruthenium bidentate phosphine complexes for the coordination and catalytic dehydrogenation of amine- and phosphine-boranes

Addition of the amine–boranes H₃B ? NH₂tBu, H₃B ? NHMe₂ and H₃B ? NH₃ to the cationic ruthenium fragment [Ru(xantphos)(PPh₃)(OH₂)H][BAr^F₄] ( 2 ; xantphos=4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene; BAr^F₄=[B{3,5‐(CF₃)₂C₆H₃}₄]^?) affords the η¹‐B? H bound amine–borane complexes [Ru(xantphos)(PPh₃)(H₃B ? NH₂tBu)H][BAr^F₄] ( 5 ), [Ru(xantphos)(PPh₃)(H₃B ? NHMe₂)H][BAr^F₄] ( 6 ) and [Ru(xantphos)(PPh₃)(H₃B ? NH₃)H][BAr^F₄] ( 7 ). The X‐ray crystal structures of 5 and 7 have been determined with [BAr^F₄] and [BPh₄] anions, respectively. Treatment of 2 with H₃B ? PHPh₂ resulted in quite different behaviour, with cleavage of the B? P interaction taking place to generate the structurally characterised bis‐secondary phosphine complex [Ru(xantphos)(PHPh₂)₂H][BPh₄] ( 9 ). The xantphos complexes 2 , 5 and 9 proved to be poor precursors for the catalytic dehydrogenation of H₃B ? NHMe₂. While the dppf species (dppf=1,1′‐bis(diphenylphosphino)ferrocene) [Ru(dppf)(PPh₃)HCl] ( 3 ) and [Ru(dppf)(η⁶‐C₆H₅PPh₂)H][BAr^F₄] ( 4 ) showed better, but still moderate activity, the agostic‐stabilised N‐heterocyclic carbene derivative [Ru(dppf)(ICy)HCl] ( 12 ; ICy=1,3‐dicyclohexylimidazol‐2‐ylidene) proved to be the most efficient catalyst with a turnover number of 76 h^?1 at room temperature.     

The Nature of the UC Double Bond: Pushing the Stability of High‐Oxidation‐State Uranium Carbenes to the Limit

Treatment of [K(BIPM^MesH)] (BIPM^Mes={C(PPh₂NMes)₂}^2?; Mes=C₆H₂‐2,4,6‐Me₃) with [UCl₄(thf)₃] (1 equiv) afforded [U(BIPM^MesH)(Cl)₃(thf)] ( 1 ), which generated [U(BIPM^Mes)(Cl)₂(thf)₂] ( 2 ), following treatment with benzyl potassium. Attempts to oxidise 2 resulted in intractable mixtures, ligand scrambling to give [U(BIPM^Mes)₂] or the formation of [U(BIPM^MesH)(O)₂(Cl)(thf)] ( 3 ). The complex [U(BIPM^Dipp)(μ‐Cl)₄(Li)₂(OEt₂)(tmeda)] ( 4 ) (BIPM^Dipp={C(PPh₂NDipp)₂}^2?; Dipp=C₆H₃‐2,6‐iPr₂; tmeda=N,N,N′,N′‐tetramethylethylenediamine) was prepared from [Li₂(BIPM^Dipp)(tmeda)] and [UCl₄(thf)₃] and, following reflux in toluene, could be isolated as [U(BIPM^Dipp)(Cl)₂(thf)₂] ( 5 ). Treatment of 4 with iodine (0.5 equiv) afforded [U(BIPM^Dipp)(Cl)₂(μ‐Cl)₂(Li)(thf)₂] ( 6 ). Complex 6 resists oxidation, and treating 4 or 5 with N‐oxides gives [{U(BIPM^DippH)(O)₂‐ (μ‐Cl)₂Li(tmeda)] ( 7 ) and [{U(BIPM^DippH)(O)₂(μ‐Cl)}₂] ( 8 ). Treatment of 4 with tBuOLi (3 equiv) and I₂ (1 equiv) gives [U(BIPM^Dipp)(OtBu)₃(I)] ( 9 ), which represents an exceptionally rare example of a crystallographically authenticated uranium(VI)–carbon σ bond. Although 9 appears sterically saturated, it decomposes over time to give [U(BIPM^Dipp)(OtBu)₃]. Complex 4 reacts with PhCOtBu and Ph₂CO to form [U(BIPM^Dipp)(μ‐Cl)₄(Li)₂(tmeda)(OCPhtBu)] ( 10 ) and [U(BIPM^Dipp)(Cl)(μ‐Cl)₂(Li)(tmeda)(OCPh₂)] ( 11 ). In contrast, complex 5 does not react with PhCOtBu and Ph₂CO, which we attribute to steric blocking. However, complexes 5 and 6 react with PhCHO to afford (DippNPPh₂)₂C?C(H)Ph ( 12 ). Complex 9 does not react with PhCOtBu, Ph₂CO or PhCHO; this is attributed to steric blocking. Theoretical calculations have enabled a qualitative bracketing of the extent of covalency in early‐metal carbenes as a function of metal, oxidation state and the number of phosphanyl substituents, revealing modest covalent contributions to U?C double bonds.     

Synthesis and Structure of a Novel Cluster with Trigonal-bipyramidal Ge_2Ru_3 Core

ＩｎｔｒｏｄｕｃｔｉｏｎＷｅｒｅｃｅｎｔｌｙｒｅｐｏｒｔｅｄａｎｉｎｔｒａｍｏｌｅｃｕｌａｒｔｈｅｒｍａｌｒｅａｒ ｒａｎｇｅｍｅｎｔｂｅｔｗｅｅｎＳｉ—ＳｉａｎｄＦｅ—Ｆｅｂｏｎｄｓｉｎｔｈｅｄｉｎｕ ｃｌｅａｒｉｒｏｎｃｏｍｐｌｅｘ { (Ｍｅ2 ＳｉＳｉＭｅ2 ) [(η5 Ｃ5Ｈ4 )Ｆｅ(ＣＯ) ]2 (μ ＣＯ) 2 } (Ｓｃｈｅｍｅ 1) .1 5Ｔｈｅｔｈｅｒｍａｌｒｅａｒｒａｎｇｅｍｅｎｔｗａｓｌａｔｅｒｅｘｔｅｎｄｅｄｔｏｇｅｒｍａｎｉｕｍ ｉｒｏｎａｎｄｓｉｌｉｃｏｎ ｒｕｔｈｅｎｉ ｕｍａｎａｌｏｇｕｅｓ .6 8Ｔｈ…     

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.     

Ruthenium(II) Complexes Bearing Schiff Base Ligands for Efficient Acceptorless Dehydrogenation of Secondary Alcohols†

Four ruthenium(II) complexes 1—4 [RN=CH‐(2,4‐(^tBu)₂C₆H₂O)]RuH(PPh₃)₂(CO) (R = C₆H₅, 1; R = 4‐MeC₆H₄, 2; R = 4‐ClC₆H₄, 3; R = 4‐BrC₆H₄, 4) bearing Schiff base ligands were prepared by treating RuHClCO(PPh₃)₃ with RN=CH‐(2,4‐(^tBu)₂C₆H₂OH (L1—L4) in the presence of triethylamine. Their structures were fully characterized by elemental analysis, IR, NMR spectroscopy and X‐ray crystallography. These Ru(II) complexes exhibit high catalytic performance and good functional‐group compatibility in the acceptorless dehydrogenation of secondary alcohols, affording the corresponding ketones in 82%—94% yields.     

Bifunctional Rhenium Complexes for the Catalytic Transfer‐Hydrogenation Reactions of Ketones and Imines

The silyloxycyclopentadienyl hydride complexes [Re(H)(NO)(PR₃)(C₅H₄OSiMe₂tBu)] (R=iPr ( 3 a ), Cy ( 3 b )) were obtained by the reaction of [Re(H)(Br)(NO)(PR₃)₂] (R=iPr, Cy) with Li[C₅H₄OSiMe₂tBu]. The ligand–metal bifunctional rhenium catalysts [Re(H)(NO)(PR₃)(C₅H₄OH)] (R=iPr ( 5 a ), Cy ( 5 b )) were prepared from compounds 3 a and 3 b by silyl deprotection with TBAF and subsequent acidification of the intermediate salts [Re(H)(NO)(PR₃)(C₅H₄O)][NBu₄] (R=iPr ( 4 a ), Cy ( 4 b )) with NH₄Br. In nonpolar solvents, compounds 5 a and 5 b formed an equilibrium with the isomerized trans‐dihydride cyclopentadienone species [Re(H)₂(NO)(PR₃)(C₅H₄O)] ( 6 a,b ). Deuterium‐labeling studies of compounds 5 a and 5 b with D₂ and D₂O showed H/D exchange at the H_Re and H_O positions. Compounds 5 a and 5 b were active catalysts in the transfer hydrogenation reactions of ketones and imines with 2‐propanol as both the solvent and H₂ source. The mechanism of the transfer hydrogenation and isomerization reactions was supported by DFT calculations, which suggested a secondary‐coordination‐sphere mechanism for the transfer hydrogenation of ketones.