Beiträge zur Chemie des Phosphors. Synthese und Eigenschaften des 1,2-Diphospha-3,4-diboretans (t-BuP)2(BNMe2)2

Contributions tot he Chemistry of Phosphorus. 148. Synthesis and Properties of the 1,2-Diphospha-3,4-diboretane (t-BuP)₂(BNMe₂)₂ The first 1, 2-diphospha-3,4-diboretane (1,2-diphospha-3, 4-diboracyclobutane) (t-BuP)₂(BNMe₂)(1) was prepared by [2+2] cyclocondensation of K(t-Bu)P? P(t-Bu)K with Cl(Me₂N)B? B(NMe₂)Cl. 1 could be isolated in the pure state and was NMR spectroscopically characterized as a compound with a planar P₂ B₂ ring skeleton.     

Phosphaniminato-Komplexe von Bor. Synthese und Kristallstrukturen von [BBr2(NPMe3)]2, [B2Br3(NPiPr3)2]Br, [B2(NPEt3)4]Br2, [B2Br2(NPPh3)3]BBr4 und [{B2(NMe2)2}2(NPEt3)2]Cl2

Phosphoraneiminato Complexes of Boron. Syntheses and Crystal Structures of [BBr₂(NPMe₃)]₂, [B₂Br₃(NPⁱPr₃)₂]Br, [B₂(NPEt₃)₄]Br₂, [B₂Br₂(NPPh₃)₃]BBr₄ and [{B₂(NMe₂)₂}₂(NPEt₃)₂]Cl The bromoderivatives of the title compounds are prepared from the corresponding silylated phosphoraneimines Me₃SiNPR₃ and boron tribromide. The boron subcompound [{B₂(NMe₂)₂}₂(NPEt₃)₂]Cl₂ derives from Me₃SiNPEt₃ and B₂Cl₂(NMe₂)₂. All complexes are characterized by NMR and IR spectroscopy as well as by crystal structure determinations. [BBr₂(NPMe₃)]₂ (1): Space group P2₁/n, Z = 2, R = 0.031. Lattice dimensions at ?50°C: a = 723.8, b = 894.2, c = 1305.4 pm, β = 92.35°. 1 forms centrosymmetric molecules in which the boron atoms are linked via μ₂-N bridges of the NPMe₃^? groups of from B₂N₂ four-membered rings with B? N distances of 149.9 and 150.9 pm. B₂Br₃(NPⁱPr₃)₂]Br (2): Space group P2₁, Z = 2, R = 0.059. Lattice dimensions at ?80°C: a = 817.6, b = 2198.7, c = 851.5 pm, β = 115.09°. In the cations of 2 the boron atoms are lined via the μ₂-N atoms of the NPⁱPr₃^? groups to form planar, asymmetric B₂N₂ four-membered rings with B? N distances of 143 and 156 pm. [B₂(NPEt₃)₄[Br₂·4CH₂Cl₂ (3): Space group C2/c, Z = 4, R = 0.042. Lattice dimensions at ?50°C: a = 1946.1, b = 1180.3, c = 2311.3 pm, β = 101.02°. The structure contains centrosymmetric dications in which both the boron atoms are lined by the N atoms of two of the NPEt₃^? groups to form a B₂N₂ four-membered ring with B? N distances of 149.6 pm. The remaining two NPEt₃^? groups are terminally bonded with very short B? N distances of 133.5 pm. B₂Br₂(NPPh₃)₃]BBr₄ (4): Space group P1 , Z = 2, R = 0.065. Lattice dimension at ?50°C: a = 1025.7, b = 1496.1, c = 1807.0 pm, α = 85.09°, β = 82.90°, γ = 82.72°. In the cation the boron atoms are lined via the μ₂-N atoms of two of the NPPh₃^? groups to form a nearly planer B₂N₂ four-membered ring with B? N distances of 149.3-153.1 pm. The third NPPh₃³ group is terminally connected with teh sp² hybridized boron atom and with a B? N distance of 134.1 pm along with an almost linear BNP bond angle of 173.6°. [{B₂(NMe₂)₂}₂(NPEt₂)₂]Cl₂ · 3CH₂Cl₂ (5): Space group C2/c, Z = 4, R = 0.098. Lattice dimensions at ?70°C: a = 1557.9, b = 1294.7, c = 2122.9 pm, β = 96.08°. The structure of 4 contains centrosymmetric dications in which two by two B-B dumb-bells are linked via the μ₂-N atoms of the two NEPt₃^? groups to form B₄N₂ six-membered rings with B? N distances of 150 and 156 pm and B-B distances of 173 pm. The B? N distances of the terminally bonded NMe₂^? groups correspond to 138 pm double bonds.     

Synthesis,Structure, Bonding,and Reactivity of Metal Complexes Comprising Diborane(4) and Diborene(2): [{Cp*Mo(CO)2}2{μ‐η2:η2‐B2H4}] and [{Cp*M(CO)2}2B2H2M(CO)4], M=Mo,W

The reaction of [(Cp*Mo)₂(μ‐Cl)₂B₂H₆] ( 1 ) with CO at room temperature led to the formation of the highly fluxional species [{Cp*Mo(CO)₂}₂{μ‐η²:η²‐B₂H₄}] ( 2 ). Compound 2, to the best of our knowledge, is the first example of a bimetallic diborane(4) conforming to a singly bridged C_s structure. Theoretical studies show that 2 mimics the Cotton dimolybdenum–alkyne complex [{CpMo(CO)₂}₂C₂H₂]. In an attempt to replace two hydrogen atoms of diborane(4) in 2 with a 2e [W(CO)₄] fragment, [{Cp*Mo(CO)₂}₂ B₂H₂W(CO)₄] ( 3 ) was isolated upon treatment with [W(CO)₅?thf]. Compound 3 shows the intriguing presence of [B₂H₂] with a short B?B length of 1.624(4) Å. We isolated the tungsten analogues of 3 , [{Cp*W(CO)₂}₂B₂H₂W(CO)₄] ( 4 ) and [{Cp*W(CO)₂}₂B₂H₂Mo(CO)₄] ( 5 ), which provided direct proof of the existence of the tungsten analogue of 2 .     

Synthesis,Structure, Bonding,and Reactivity of Metal Complexes Comprising Diborane(4) and Diborene(2): [{Cp*Mo(CO)2}2{μ‐η2:η2‐B2H4}] and [{Cp*M(CO)2}2B2H2M(CO)4], M=Mo,W

The reaction of [(Cp*Mo)₂(μ‐Cl)₂B₂H₆] ( 1 ) with CO at room temperature led to the formation of the highly fluxional species [{Cp*Mo(CO)₂}₂{μ‐η²:η²‐B₂H₄}] ( 2 ). Compound 2, to the best of our knowledge, is the first example of a bimetallic diborane(4) conforming to a singly bridged C_s structure. Theoretical studies show that 2 mimics the Cotton dimolybdenum–alkyne complex [{CpMo(CO)₂}₂C₂H₂]. In an attempt to replace two hydrogen atoms of diborane(4) in 2 with a 2e [W(CO)₄] fragment, [{Cp*Mo(CO)₂}₂ B₂H₂W(CO)₄] ( 3 ) was isolated upon treatment with [W(CO)₅⋅thf]. Compound 3 shows the intriguing presence of [B₂H₂] with a short B−B length of 1.624(4) Å. We isolated the tungsten analogues of 3 , [{Cp*W(CO)₂}₂B₂H₂W(CO)₄] ( 4 ) and [{Cp*W(CO)₂}₂B₂H₂Mo(CO)₄] ( 5 ), which provided direct proof of the existence of the tungsten analogue of 2 .     

Preparation and Structure of [Me3N(CF3)2BCCB(CF3)2NMe3]

Bis‐trimethylamine‐ethynyl‐di‐bis(trifluoromethyl)borane [Me₃N(CF₃)₂BCCB(CF₃)₂NMe₃] ( 1 ) has been prepared from trimethylamine‐ethynyl‐bis(trifluoromethyl)borane, [HCCB(CF₃)₂NMe₃], and dimethylamino‐bis(trifluoromethyl)borane, (CF₃)₂BNMe₂. The structure of 1 has been determined by x‐ray crystallography. In the solid state the molecule possesses crystallographic C_i symmetry. The acetylenic attachment to the boron atom is characterized by a short B–C bond length of 1.565(4) Å and an essentially linear B–C–C′ bond angle of 178.1(4)°.     

Darstellung und Kristallstruktur von [P(C6H5)4][2,9-{N,N′-(2-NH?(C5H4N))}B10H8]

Synthesis and Crystal Structure of [P(C₆H₅)₄][2,9-{N,N′-(2-NH? (C₅H₄N))}B₁₀H₈] [N(C₄H₉)₄]₂[B₁₀H₁₀] reacts with 2-aminopyridine forming a product mixture from which [2,9-{N,N′-(2-NH? (C₅H₄N))}B₁₀H₈]^? can be isolated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose. The crystal structure of [P(C₆H₅)₄][2,9-{N,N′-(2-NH? (C₅H₄N))}B₁₀H₈] (triclinic, space group P1 , a = 10.1103(9), b = 11.5665(9), c = 14.877(2) Å, α = 102.600(8), β = 107.567(8) und γ = 96.487(7)°, Z = 2) reveals the bonding of 2-NH₂-(C₅H₄N) via both N atoms to vicinal B atoms of the two square planes of the B₁₀ cluster (B2? N1 = 1,541(7) und B9? N2 = 1.505(7) Å) forming a five-membered ring.     

Über die Reaktion von Cp2TiCl2 mit [C(NMe2)3][(CO)4FeC(O)NMe2] – Kristallstruktur von [C(NMe2)3]2[FeCl4]

Concerning the Reaction of Cp₂TiCl₂ with [C(NMe₂)₃][(CO)₄FeC(O)NMe₂] – Crystal Structure of [C(NMe₂)₃]₂[FeCl₄] The title compound forms by the reaction of Cp₂TiCl₂ with [C(NMe₂)₃][(CO)₄FeC(O)NMe₂] in THF solution. It crystallizes in the space group Pbcn with a = 1 566.6(3); b = 976.4(2); c = 1 580.4(4) pm; Z = 4; R = 3.8%. Each [FeCl₄]^2? in is surrounded by eight cations. Two cations each are connected with one Cl atom by relatively short H …? Cl contacts leading to a distortion of the tetrahedral geometry of the anion.     

Kristallstruktur von Tetraphenylphosphonium-Monothiocyanatohydro-closo-Decaborat, [P(C6H5)4]2[2-(SCN)B10H9] · CH3CN

Crystal Structure of Tetraphenylphosphonium Monothiocyanatohydro-closo-Decaborate, [P(C₆H₅)₄]₂[2-(SCN)B₁₀H₉] · CH₃CN The X-ray structure determination of [P(C₆H₅)₄]₂[2-(SCN)B₁₀H₉] · CH₃CN (monoclinic, space group P2₁/n, a = 10.6040(10), b = 13.8880(9), c = 33.888(3) Å, β = 94.095(8)°, Z = 4) reveals the S coordination of the SCN substituent with a B? S distance of 1.913(6) Å and a B? S? C angle of 105.3(3)°. The SCN group is nearly linear (178.2(7)°).     

Synthesis and Structure of 1,2-Diphenyl-1,2-disila-closo-dodecaborane(12), Reaction with [Zr(NMe2)4] and [Ta(NMe2)5]

Diphenyl-o-silaborane ( 1 ) can be obtained by sublimation as colourless crystalline material in a yield of 23%. The disilaborane 1 was characterized by NMR spectroscopy, mass spectrometry and X-ray structure analysis. The neutral closo cluster 1 reacts with [Zr(NMe₂)₄] or [Ta(NMe₂)₅] to give the dimethylamide adduct [(Me₂N)(PhSi)₂B₁₀H₁₀]^– of the disilaborane.     

Synthese und Kristallstruktur von [C(NMe2)3]2[(CO)4Fe(μ‐InCl2)2Fe(CO)4]

Synthesis and Crystal Structure of [C(NMe₂)₃]₂[(CO)₄Fe(μ‐InCl₂)₂Fe(CO)₄] Treatment of [C(NMe₂)₃]₂[(CO)₄FeInCl₃] ( 1 ) with hot water produces the dinuclear complex [C(NMe₂)₃]₂[(CO)₄Fe(μ‐InCl₂)₂Fe(CO)₄] ( 2 ) which could be crystallized from dichloromethane/pentane. 2 crystallizes in the monoclinic space group P2₁/n with a = 835.7(1), b = 1187.8(1), c = 1902.7(1) pm, β = 91.877(5)° and Z = 2. The anion contains a four‐membered Fe—In—Fe—In ring with octahedral environment at the iron atom and tetrahedral coordination at the In atom.     

Synthesis and Characterization of the Chain Borosulfates (NH4)3[B(SO4)3] and Sr[B2(SO4)4]

Two new borosulfates were obtained either by an open vessel synthesis from sulfuric acid and B(OH)₃, yielding (NH₄)₃[B(SO₄)₃] or from solvothermal synthesis in oleum enriched sulfuric acid and B(OH)₃, yielding Sr[B₂(SO₄)₄]. (NH₄)₃[B(SO₄)₃] crystallizes homeotypic to K₃[B(SO₄)₃] in space group Ibca (Z = 8, a = 728.58(3) pm, b = 1470.84(7) pm, c = 2270.52(11) pm), comprising open branched vierer single chains {¹_∞[B(SO₄)₂(SO₄)_2/2]^3–}. Sr[B₂(SO₄)₄] crystallizes as an ordered variant of Pb[B₂(SO₄)₄] in space group Pnna (Z = 4, a = 1257.4(4) pm, b = 1242.1(4) pm, c = 731.9(2) pm), consisting of loop branched vierer single chains {¹_∞[B(SO₄)_4/2]^2–}. Vibrational spectroscopy confirms both refined structure models. Thermal analysis of the dried powders, showed a decomposition towards the binary and ternary components, whereas a thermal treatment in the presence of the mother liquor promotes a decomposition of Sr[B₂(SO₄)₄] towards Sr[B₂O(SO₄)₃].     

Stabilization of Classical [B2H5]−: Structure and Bonding of [(Cp*Ta)2(B2H5)(μ‐H)L2] (Cp*=η5‐C5Me5; L=SCH2S)

The room‐temperature reaction of [Cp*TaCl₄] with LiBH₄?THF followed by addition of S₂CPPh₃ results in pentahydridodiborate species [(Cp*Ta)₂(μ,η²:η²‐B₂H₅)(μ‐H)(κ²,μ‐S₂CH₂)₂] ( 1 ), a classical [B₂H₅]^? ion stabilized by the binuclear tantalum template. Theoretical studies and bonding analysis established that the unusual stability of [B₂H₅]^? in 1 is mainly due to the stabilization of sp²‐B center by electron donation from tantalum. Reactions to replace the hydrogens attached to the diborane moiety in 1 with a 2 e {M(CO)₄} fragment (M=Mo or W) resulted in simple adducts, [{(Cp*Ta)(CH₂S₂)}₂(B₂H₅)(H){M(CO)₃}] ( 6 : M=Mo and 7 : M=W), that retained the diborane(5) unit.     

Three sulfur‐containing diborane(4) compounds

The preparation and structures of three diborane(4) compounds are described. The compound B₂(3,4‐S₂C₄H₂‐1‐S)₂ [2,2′‐bi(1,3,5,2‐tri­thia­borapentalene), C₈H₄B₂S₆] is planar and lies at a crystallographic inversion centre. The amine adducts [B₂(C₃S₅)₂(NHMe₂)₂] [2,2′‐bis­(di­methyl­amino)‐2,2′‐bi(1,3,4,6,2‐tetra­thia­borapentalene‐5‐thione), C₁₀H₁₄B₂N₂S₁₀] and [B₂(1,2‐S₂C₂H₄)₂(NHMe₂)₂]·0.33CH₂Cl₂ [1,2‐bis­(di‐methylamino)‐1,1:2,2‐bis(dimethylenedithioxy)diborane(4) di­chloro­methane solvate, C₈H₂₂B₂N₂S₄·0.33CH₂Cl₂] contain di­methyl­amine ligands bound to each boron in an anti conformation about the B—B bond, with tetrahedral geometry at the B atoms. The crystal structures display a number of S?S interactions, which appear to dictate the packing arrangements.     

Beiträge zur Chemie des Phosphors. 245 [1], LiP7(BNEt2)2 und P7(BNEt2)4Cl: Zwei neuartige polycyclische Boraphosphane

Contributions to the Chemistry of Phosphorus. 245, LiP₇(BNEt₂)₂ and P₇(BNEt₂)₄Cl: Two Novel Polycyclic Boraphosphanes The directed synthesis of a noval tetracyclic heteropolyphosphane skeleton from a tricyclophosphane has been achieved by condensation of Li₃P₇ · 3DME with Cl(Et₂N)B‐B(NEt₂)Cl to the diboranonaphosphanide LiP₇(BNEt₂)₂ ( 1 ). When the reaction proceeds the mixed‐substituted diboranonaphosphane P₇(BNEt₂)₄Cl ( 2 ) is formed. According to their ³¹P NMR spectra 1 and 2 possess a B₂P₇(3) skeleton analogous to that of the hydrocarbon deltacyclane. Additional weak signals in the ³¹P NMR spectrum of 2 indicate that also small amounts of the symmetrically substituted diborane(4) P₁₄B₆(NEt₂)₆ ( 3 ) are formed.     

Über die Reaktionen von CH2=P(NMe2)3 mit Fe(CO)5, Cr(CO)6 und CS2; Molekülstrukturen von [MeP(NMe2)3][(CO)5CrC(O)CH=P(NMe2)3] und (CO)4Fe=C(OMe)CH=P(NMe2)3

The Reactions of CH₂=P(NMe₂)₃ with Fe(CO)₅, Cr(CO)₆, and CS₂; Molecular Structures of [MeP(NMe₂)₃][(CO)₅CrC(O)CH=P(NMe₂)₃], and (CO)₄Fe=C(OMe)CH=P(NMe₂)₃ The ylide CH₂=P(NMe₂)₃ ( 1 ) reacts with several binary transition metal carbonyls M(CO)_x to produce the corresponding salt like compounds [MeP(NMe₂)₃][(CO)_x–1MC(O)CH=P(NMe₂)₃] (M = Fe ( 3 ), Cr ( 4 )). The related reaction with CS₂ leads to the salt [MeP(NMe₂)₃][SC(S)CH=P(NMe₂)₃] ( 2 ). While 4 is thermally stable, 3 rapidly decomposes at room temperature with formation of [MeP(NMe₂)₃]₂[Fe₂(CO)₈] ( 8 ). Alkylation of 3 (at –50 °C) and 4 with MeSO₃CF₃ produces the related carbene complexes (CO)_x–1M=C(OMe)CH=P(NMe₂)₃ ( 5 ) and ( 6 ); the reaction of 3 with Me₃SiCl results in the formation of the carbene complex (CO)₄Fe=C(OSiMe₃)CH=P(NMe₂)₃ ( 7 ). 4 crystallizes in the space group P2₁2₁2₁ (No. 19) with a = 1111.1(2), b = 1476.1(3), c = 1823.1(4) pm and Z = 4. 5 crystallizes in the space group P2₁/n (No. 14) with a = 1303.6(3), b = 910.5(4), c = 1627.0(4) pm, β = 96.06(2)° and Z = 4. The compounds have been characterized by elemental analyses, NMR (¹H, ¹³C, ³¹P) and IR spectroscopy.     

[2+4] and [2+2] Cycloaddition Reactions of N‐Sulfinyl Carboxylic Acid Amides with (CF3)2BNMe2. Crystal Structure of cyclo‐(CF3)2B‐NMe2‐S(=O)‐N=C(p‐CH3C6H4)‐O

N‐sulfinylacylamides R‐C(=O)‐N=S=O react with (CF₃)₂BNMe₂ ( 1 ) to form, by [2+4] cycloaddition, six‐membered rings cyclo‐(CF₃)₂B‐NMe₂‐S(=O)‐N=C(R)‐O for R = Me ( 2 ), t‐Bu ( 3 ), C₆H₅ ( 4 ), and p‐CH₃C₆H₄ ( 5 ) while N‐sulfinylcarbamic acid esters R‐O‐C(=O)‐N=S=O react with 1 to yield mixtures of six‐membered (cyclo‐(CF₃)₂B‐NMe₂‐S(=O)‐N=C(OR)‐O) and four‐membered rings (cyclo‐(CF₃)₂B‐NMe₂‐S(=O)‐N(C=O)OR) for R = Me ( 6 and 9 ), Et ( 7 and 10 ), and C₆H₅ ( 8 and 11 ). The structure of 5 has been determined by X‐ray diffraction.     

Niob- und Tantalkomplexe mit P2- und P4-Liganden

Niobium and Tantalum Complexes with P₂ and P₄ Ligands The photolysis of [Cp″Ta(CO)₄] 1 (Cp″ = C₅H₃^tBu₂?1,3) and P₄ affords Cp″(CO)₂Ta(η⁴?P₄) 2 , [{Cp″(CO)Ta}₂(m??η^2:2?P₂)₂] 3 and [Cp₃″(CO)₃Ta₃(P₂)₂] 4 . In a photochemical reaction 2 and [Cp*Nb(CO)₄] 5 form [{Cp*(CO)Nb}{Cp″(CO)Ta}(m??η^2:2?P₂)₂] 6 and [{Cp*(CO)₂Nb} {Cp*Nb}{Cp″(CO)Ta}(m?₃?η^2:1:1?P₂)₂] 7 , a compound with the novel m?₃?η^2:2:1?P₂-coordination mode. The reaction of 2 and [Cp*Co(C₂H₄)₂] 8 leads to [{Cp*Co} {Cp″(CO)Ta}(m??η^2:2?P₂)₂] 9 , a heteronuclear complex with an ?early”? and a ?late”? transition metal. Complexes 2, 3, 7 and 9 have been further characterized by X-ray structure analyses.     

Synthesis and structural characterization of ferrocene-based bis(pyrazol-1-yl)borate ligands: FcB(Me)pz2K, Fc2Bpz2K, and 1,1′-fc[B(Me)pz2]2K2 (Fc: ferrocenyl, fc: ferrocenylene, pz: pyrazolyl)

Reaction of the ferrocenyl(dimethylamino)boranes FcB(Me)NMe₂, Fc₂BNMe₂, and 1,1′-fc[B(Me)NMe₂]₂ with 1:1 mixtures of pyrazole and potassium pyrazolide in refluxing THF gave the potassium salts of the ferrocene-based bis(pyrazol-1-yl)borate ligands FcB(Me)pz₂K, Fc₂Bpz₂K, and 1,1′-fc[B(Me)pz₂]₂K₂ in good yield (Fc: ferrocenyl, fc: ferrocenylene, pz: pyrazolyl). In the solid state, FcB(Me)pz₂K and Fc₂Bpz₂K form centrosymmetric dimers with short K?Cp contacts suggesting an η⁵ coordination mode of the potassium ion. The crystal lattice of the ditopic ligand 1,1′-fc[B(Me)pz₂]₂K₂ consists of coordination polymer strands featuring essentially the same structural motif that has been observed for the monotopic derivatives. All three scorpionate ligands are thus promising building blocks for the preparation of ferrocene-containing multiple-decker sandwich complexes.     

Ir(PCy3)2(H)2(H2B-NMe2)]+ as a latent source of aminoborane: probing the role of metal in the dehydrocoupling of H3B⋅NMe2H and retrodimerisation of [H2BNMe2]2

The Ir^III fragment {Ir(PCy₃)₂(H)₂}⁺ has been used to probe the role of the metal centre in the catalytic dehydrocoupling of H₃B?NMe₂H ( A ) to ultimately give dimeric aminoborane [H₂BNMe₂]₂ ( D ). Addition of A to [Ir(PCy₃)₂(H)₂(H₂)₂][BAr^F₄] ( 1 ; Ar^F=(C₆H₃(CF₃)₂), gives the amine‐borane complex [Ir(PCy₃)₂(H)₂(H₃B?NMe₂H)][BAr^F₄] ( 2 a ), which slowly dehydrogenates to afford the aminoborane complex [Ir(PCy₃)₂(H)₂(H₂B? NMe₂)][BAr^F₄] ( 3 ). DFT calculations have been used to probe the mechanism of dehydrogenation and show a pathway featuring sequential BH activation/H₂ loss/NH activation. Addition of D to 1 results in retrodimerisation of D to afford 3 . DFT calculations indicate that this involves metal trapping of the monomer–dimer equilibrium, 2 H₂BNMe₂ ? [H₂BNMe₂]₂. Ruthenium and rhodium analogues also promote this reaction. Addition of MeCN to 3 affords [Ir(PCy₃)₂(H)₂(NCMe)₂][BAr^F₄] ( 6 ) liberating H₂B? NMe₂ ( B ), which then dimerises to give D . This is shown to be a second‐order process. It also allows on‐ and off‐metal coupling processes to be probed. Addition of MeCN to 3 followed by A gives D with no amine‐borane intermediates observed. Addition of A to 3 results in the formation of significant amounts of oligomeric H₃B?NMe₂BH₂?NMe₂H ( C ), which ultimately was converted to D . These results indicate that the metal is involved in both the dehydrogenation of A , to give B , and the oligomerisation reaction to afford C . A mechanism is suggested for this latter process. The reactivity of oligomer C with the Ir complexes is also reported. Addition of excess C to 1 promotes its transformation into D , with 3 observed as the final organometallic product, suggesting a B? N bond cleavage mechanism. Complex 6 does not react with C , but in combination with B oligomer C is consumed to eventually give D , suggesting an additional role for free aminoborane in the formation of D from C .     

Cu[B2(SO4)4] and Cu[B(SO4)2(HSO4)]—Two Silicate Analogue Borosulfates Differing in their Dimensionality: A Comparative Study of Stability and Acidity

Borosulfates are an ever‐expanding class of compounds and the extent of their properties is still elusive. Herein, the first two copper borosulfates Cu[B₂(SO₄)₄] and Cu[B(SO₄)₂(HSO₄)] are presented, which are structurally related but show different dimensionalities in their substructure: While Cu[B₂(SO₄)₄] reveals an anionic chain, [B(SO₄)_4/2]^?, with both a twisted and a unique chair conformation of the B(SO₄)₂B subunits, Cu[B(SO₄)₂(HSO₄)] reveals isolated [B₂(SO₄)₄(HSO₄)₂]^4? anions showing exclusively a twisted conformation. The complex anion can figuratively be obtained as a cut‐out from the anionic chain by protons. Comparative DFT calculations based on magnetochemical measurements complement the experimental studies. Calculation of the pK_a values of the two conformers of the [B₂(SO₄)₄(HSO₄)₂]^4? anion revealed them to be more similar to silicic than to sulfuric acid, highlighting the close relationship to silicates.