Syntheses and characterization of new vinyl-borylene complexes by the hydroboration of alkynes with [(μ3-BH)(Cp*RuCO)2(μ-CO)Fe(CO)3]

From trihydroborates to bisborylenes: a route to dinuclear bisborylene complexes

A new route for the synthesis of dinuclear bisborylene complexes was described. A series of novel diruthenium bisborylenes were prepared through unprecedented triple B-H oxidative addition of trihydroborates with concomitant hydrogen liberation. Conversion of trihydroborates to bisborylenes involved the formation of tris(σ-B-H) borate as the crucial intermediate stage.

Heterometallic Triply-Bridging Bis-Borylene Complexes

Triply-bridging bis-{hydrido(borylene)} and bis-borylene species of groups 6, 8 and 9 transition metals are reported. Mild thermolysis of [Fe₂ (CO)₉ ] with an in situ produced intermediate, generated from the low-temperature reaction of [Cp*WCl₄ ] (Cp*=η⁵ -C₅ Me₅ ) and [LiBH₄ ⋅THF] afforded triply-bridging bis-{hydrido(borylene)}, [(μ₃ -BH)₂ H₂ {Cp*W(CO)₂ }₂ {Fe(CO)₂ }] (1) and bis-borylene, [(μ₃ -BH)₂ {Cp*W(CO)₂ }₂ {Fe(CO)₃ }] (2). The chemical bonding analyses of 1 show that the B-H interactions in bis-{hydrido (borylene)} species is stronger as compared to the M-H ones. Frontier molecular orbital analysis shows a significantly larger energy gap between the HOMO-LUMO for 2 as compared to 1. In an attempt to synthesize the ruthenium analogue of 1, a similar reaction has been performed with [Ru₃ (CO)₁₂ ]. Although we failed to get the bis-{hydrido(borylene)} species, the reaction afforded triply-bridging bis-borylene species [(μ₃ -BH)₂ {WCp*(CO)₂ }₂ {Ru(CO)₃ }] (2'), an analogue of 2. In search for the isolation of bridging bis-borylene species of Rh, we have treated [Co₂ (CO)₈ ] with nido-[(RhCp*)₂ (B₃ H₇ )], which afforded triply-bridging bis-borylene species [(μ₃ -BH)₂ (RhCp*)₂ Co₂ (CO)₄ (μ-CO)] (3). All the compounds have been characterized by means of single-crystal X-ray diffraction study; ¹ H, ¹¹ B, ¹³ C NMR spectroscopy; IR spectroscopy and mass spectrometry.

Toward Transition-Metal-Templated Construction of Arylated B4 Chains by Dihydroborane Dehydrocoupling

The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH₂ ] (Dur=2,3,5,6-Me₄ C₆ H) and [(Me₃ Si)₂ NBH₂ ] led to the formation of bridging borylene complexes of the form [(Cp*RuH)₂ BR] (Cp*=C₅ Me₅ ; 1 a: R=Dur; 1 b: R=N(SiMe₃ )₂ ) through oxidative addition of the B-H bonds with concomitant hydrogen liberation. Employing the more electron-deficient dihydroborane [3,5-(CF₃ )₂ -C₆ H₃ BH₂ ] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF)₄ [(Cp*Ru)₂ B₄ H₅ (3,5-(CF₃ )₂ C₆ H₃ )₄ ] (4), through an unusual, incomplete threefold dehydrocoupling process. A comparative theoretical investigation of the bonding in a simplified model of 4 and the analogous complex nido-[1,2(Cp*Ru)₂ (μ-H)B₄ H₉ ] (I) indicates that there appear to be no classical σ-bonds between the boron atoms in complex I, whereas in the case of 4 the B₄ chain better resembles a network of three B-B σ bonds, the central bond being significantly weaker than the other two.

Five-Membered Ruthenacycles: Ligand-Assisted Alkyne Insertion into 1,3-N,S-Chelated Ruthenium Borate Species

Building upon previous work, the chemistry of [(η⁶ -p-cymene)Ru{P(OMe)₂ OR}Cl₂ ], (R=H or Me) has been extended with [H₂ B(mbz)₂ ]^- (mbz=2-mercaptobenzothiazolyl) using different Ru precursors and borate ligands. As a result, a series of 1,3-N,S-chelated ruthenium borate complexes, for example, [(κ² -N,S-L)PR₃ Ru{κ³ -H,S,S'-H₂ B(L)₂ }], (2 a-d and 2 a'-d'; R=Ph, Cy, OMe or OPh and L=C₅ H₄ NS or C₇ H₄ NS₂ ) and [Ru{κ³ -H,S,S'-H₂ B(L)₂ }₂ ], (3: L=C₅ H₄ NS, 3': L=C₇ H₄ NS₂ ) were isolated upon treatment of [(η⁶ -p-cymene)RuCl₂ PR₃ ], 1 a-d (R=Ph, Cy, OMe or OPh) with [H₂ B(mp)₂ ]^- or [H₂ B(mbz)₂ ]^- ligands (mp=2-mercaptopyridyl). All the Ru borate complexes, 2 a-d and 2 a'-d' are stabilized by phosphine/phosphite and hemilabile N,S-chelating ligands. Treatment of these Ru borate species, 2 a'-c' with various terminal alkynes yielded two different types of five-membered ruthenacycle species, namely [PR₃ {C₇ H₄ S₂ -(E)-N-C=CH(R')}Ru{κ³ -H,S,S'-H₂ B(L)₂ }], (4-4'; R=Ph and R'=CO₂ Me or C₆ H₄ NO₂ ; L=C₇ H₄ NS₂ ) and [PR₃ {C₇ H₄ NS-(E)-S-C=CH(R')}Ru{κ³ -H,S,S'-H₂ B(L)₂ }], (5-5', 6 and 7; R=Ph, Cy or OMe and R'=CO₂ Me or C₆ H₄ NO₂ ; L=C₇ H₄ NS₂ ). All these five-membered ruthenacycle species contain an exocyclic C=C moiety, presumably formed by the insertion of a terminal alkyne into the Ru-N and Ru-S bonds. The new species have been characterized spectroscopically and the structures were further confirmed by single-crystal X-ray diffraction analysis. Theoretical studies and chemical-bonding analyses established that charge transfer occurs from phosphorus to ruthenium center following the trend PCy₃ <PPh₃ <P(OPh)₃ <P(OMe)₃ .

Synthesis of Trithia-Borinane Complexes Stabilized in Diruthenium Core: [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3BR}] (R = H or SMe)

The thermolysis of arachno-1 [(Cp*Ru)2(B3H8)(CS2H)] in the presence of tellurium powder yielded a series of ruthenium trithia-borinane complexes: [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3BH}] 2, [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3B(SMe)}] 3, and [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3BH}] 4. Compounds 2–4 were considered as ruthenium trithia-borinane complexes, where the central six-membered ring {C2BS3} adopted a boat conformation. Compounds 2–4 were similar to our recently reported ruthenium diborinane complex [(Cp*Ru){(η2-SCHS)CH2S2(BH2)2}]. Unlike diborinane, where the central six-membered ring {CB2S3} adopted a chair conformation, compounds 2–4 adopted a boat conformation. In an attempt to convert arachno-1 into a closo or nido cluster, we pyrolyzed it in toluene. Interestingly, the reaction led to the isolation of a capped butterfly cluster, [(Cp*Ru)2(B3H5)(CS2H2)] 5. All the compounds were characterized by 1H, 11B{1H}, and 13C{1H} NMR spectroscopy and mass spectrometry. The molecular structures of complexes 2, 3, and 5 were also determined by single-crystal X-ray diffraction analysis.

Mercapto-benzothiazolyl based ruthenium(ii) borate complexes: synthesis and reactivity towards various phosphines

Ruthenium complexes featuring phosphinate and dual Ru⋯H–B interactions between Ru and B–H bonds of borate ligands supported by mercapto-benzothiazolyl heterocycles have been synthesized.

Highly efficient and selective hydroboration of terminal and internal alkynes catalysed by a cobalt(ii) coordination polymer

Selective hydroboration of terminal and internal alkynes is catalysed using a Co^II-coordination polymer precatalyst with TOFs of up to 47 520 h⁻¹.

An Efficient Method for the Synthesis of Boratrane Complexes of Late Transition Metals

In a quest for efficient precursors for the synthesis of boratrane complexes of late transition metals, we have developed a useful synthetic method using [L'M(μ-Cl)Cl_x ]₂ as precursors (L'=η⁶ -p-cymene, M=Ru, x=1; L'=COD, M=Rh, x=0 and L'=Cp*, M=Ir or Rh, x=1; COD=1,5-cyclooctadiene, Cp*=η⁵ -C₅ Me₅ ). For example, treatment of Na[(H₃ B)bbza] or Na[(H₂ B)mp₂ ] (bbza=bis(benzothiazol-2-yl)amine; mp=2-mercaptopyridyl) with [L'M(μ-Cl)Cl_x ]₂ yielded [(η⁶ -p-cymene)RuBH{(NCSC₆ H₄ )(NR)}₂ ] (2; R=NCSC₆ H₄ ), [{N(NCSC₆ H₄ )₂ }RhBH{(NCSC₆ H₄ )(NR)}₂ ] (3; R=NCS-C₆ H₄ ), [(η⁶ -p-cymene)RuBH(L)₂ ] (5; L=C₅ H₄ NS), and [Cp*MBH(L)₂ ] (6 and 7; L=C₅ H₄ NS, M=Ir or Rh). In order to delineate the significance of the ligands, we studied the reactivity of [(COD)Rh(μ-Cl)]₂ with Na[(H₃ B)bbza], which led to the formation of the isomeric agostic complexes [(η⁴ -COD)Rh(μ-H)BHRh(C₁₄ H₈ N₃ S₂ )₃ ], 4 a and 4 b, in parallel to the formation of 16-electron square-pyramidal rhodaboratrane complex 3. Compounds 4 a and 4 b show two different geometries, in which the Rh-B bonds are shorter than in the reported Rh agostic complexes. The new compounds have been characterized in solution by various spectroscopic analyses, and their structural arrangements have been unequivocally established by crystallographic analyses. DFT calculations provide useful insights regarding the stability of these metallaboratrane complexes as well as their M→B bonding interactions.

Design, Synthesis, and Chemistry of Bis(σ)borate and Agostic Complexes of Group 7 Metals

A series of new bis(σ)borate and agostic complexes of group 7 metals have been synthesized and structurally characterized from various borate ligands, such as trihydrobis(benzothiazol-2-yl)amideborate (Na[(H₃ B)bbza]), trihydro(2-aminobenzothiazolyl)borate (Na[(H₃ B)abz]), and dihydrobis(2-mercaptopyridyl)borate (Na[(H₂ B)mp₂ ]) (bbza=bis(benzothiazol-2-yl)amine, abz=2-aminobenzothiazolyl, and mp=2-mercaptopyridyl). Photolysis of [Mn₂ (CO)₁₀ ] with Na[(H₃ B)bbza] formed bis(σ)borate complex [Mn(CO)₃ (μ-H)₂ BHNCSC₆ H₄ (NR)] (1; R=NCSC₆ H₄ ). Octahedral complex [Re(CO)₂ (N₃ C₂ S₂ C₁₂ H₈ )₂ ] (2) was generated under similar reaction conditions with [Re₂ (CO)₁₀ ]. Similarly, when [Mn₂ (CO)₁₀ ] was treated with Na[(H₃ B)abz], bis(σ)borate complex [Mn(CO)₃ (μ-H)₂ BH(HN₂ CSC₆ H₄ )] (3) and the agostic complex [Mn(CO)₃ (μ-H)BH(HN₂ CSC₆ H₄ )₂ ] (4) were formed. To probe the potential formation of agostic complexes of the heavier group 7 metals, we carried out the photolysis of [M₂ (CO)₁₀ ] with Na[(H₂ B)mp₂ ] and found that [M(CO)₃ (μ-H)BH(C₅ H₄ NS)₂ ] (5: M=Re; 6: M=Mn) was formed in moderate yield. Complexes 1 and 3 feature a (κ³ -H,H,N) coordination mode, whereas 4, 5, and 6 display both (κ³ -H,N,N) and (κ³ -H,S,S) modes of the corresponding ligands. To investigate the lability of the CO ligands of 1 and 3, we treated the complexes with phosphine ligands that generated novel bis(σ)borate complexes [Mn(μ-H)₂ (BHNCSC₆ H₄ )(NR)(CO)₂ PL₂ L'] (R=NCSC₆ H₄ ; 7 a: L=L'=Ph; 7 b: L=Ph, L'=Me) and [Mn(μ-H)₂ BHN(NCSC₆ H₄ )R(CO)₂ PL₂ L'] (R=NCSC₆ H₄ ; 8 a: L=L'=Ph; 8 b: L=Ph, L'=Me). Complexes 7 and 8 are structural isomers with different coordination modes of the bbza ligand. In addition, DFT calculations were performed to shed some light on the bonding and electronic structures of these complexes.

Hypo-electronic triple-decker sandwich complexes: synthesis and structural characterization of [(Cp*Mo)2{μ–η6:η6-B4H4E-Ru(CO)3}] (E = S, Se, Te or Ru(CO)3 and Cp* = η5-C5Me5)

Electron-poor triple-decker complexes, [(Cp*Mo)₂{μ–η⁶:η⁶-B₄H₄ERu(CO)₃}] (E = S, Se, Te, Ru(CO)₃) with hexagonal bridging ring composed of boron, ruthenium and chalcogen atoms.

Editorial of Special Issue Ruthenium Complex: The Expanding Chemistry of the Ruthenium Complexes

Recent trends in Ru complex chemistry are surveyed with emphasis on the development of anticancer drugs and applications in catalysis, polymers, materials science and nanotechnology.

Homometallic Cubane Clusters: Participation of Three-Coordinated Hydrogen in 60-Valence Electron Cubane Core

This work describes the synthesis, structural characterizations, and electronic structures of a series of novel homometallic cubane clusters [(Cp*Ru)2{Ru(CO)2}2BH(μ3-E)(μ-H)B(μ-H)3M], (2, M = Cp*Ru, E = CO; 3, M = Ru(Cp*Ru)2(μ-CO)3(μ-H)BH), E = BH), [(Cp*Ru)3(μ3-CO)(BH)3(μ3-H)3], 4, and [(Cp*Ru)2(μ3-CO){Ru(CO)3}2(BH)2(μ-H)B], 5 (Cp* = η(5)-C5Me5). These cubane clusters have been isolated from a thermally driven reaction of diruthenium analogue of pentaborane(9) [(Cp*RuH)2B3H7], 1, and [Ru3(CO)12]. Structural and spectroscopic studies revealed the existence of triply bridged hydrogen (μ3-H) atoms that participate as a vertex in the cubane core formation for compounds 2, 3, and 4. In addition, the crystal structure of these clusters clearly confirms the presence of an electron precise borane ligand (borylene fragment) which is triply bridged to the trimetallic units. Bonding of these novel complexes has been studied computationally by DFT methods, and the studies demonstrate that the cubane clusters 2 and 3 possess 60 cluster valence electrons (cves) with six metal-metal bonds. All the new compounds have been characterized in solution by mass spectrometry; IR; and (1)H, (11)B, and (13)C NMR studies, and the structural types were unequivocally established by crystallographic analysis of compounds 2-5.

Side-on coordination of boryl and borylene complexes to cationic coinage metal fragments

The M-(η2-BMn) complex [(η5-C5H5)(OC)2Mn{μ-B(Cl)(tBu)Au(PPh3)}] (2) can be functionalized via halide substitution reactions to afford isostructural complexes [(η5-C5H5)(OC)2Mn{μ-B(R)(tBu)Au(PPh3)}] (R = Ph, CCPh and NCS). It also reacts with coinage metal complexes [MCl(PPh3)] (M = Au, Ag and Cu) in the presence of halide abstraction reagents to afford borylene-bridged heteromultinuclear complexes [{(η5-C5H5)(OC)2Mn}2{μ2-B(tBu)}2M][BArx4] (M = Au, Ag and Cu; Arx = 3,5-C6H3Cl2, 3,5-C6H3(CF3)2). Experimental characterization as well as computational studies revealed that these complexes are best viewed as transition metal borylene complexes side-on coordinated to monovalent coinage metal cations, thus representing the first boron analogs of Stone's alkylidyne-bridged multinuclear complexes.

Synthesis, characterization and crystal structure analysis of cobaltaborane and cobaltaheteroborane clusters

A novel class of cobaltaborane and cobaltaheteroborane clusters, isocloso-[(Cp*Co)₃B₆H₇Co(CO)₂], closo-[(Cp*Co)₂B₂H₅Mo₂(CO)₆I], nido-[(Cp*Co)₂B₂H₂S₂], and closo-[(Cp*Co)₂B₄H₂Br₄] were investigated (see picture).