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In an effort to explore the coordination chemistry of the coordinative sulfur centers in arachno-ruthenaborane [(Cp*Ru)2(B3H8)(CS2H)] (arachno-1), we have thermolyzed arachno-1 with group-6 metal carbonyls [M(CO)5·THF] (M = Cr, Mo and W). The reaction of arachno-1 with [Cr(CO)5·THF] resulted in the formation of hetero-trimetallic triply bridging borylene [(Cp*Ru)2(μ-CO)(μ3-CH2S2-κ2S′:κ2S′′){Cr(CO)3}(μ3-BH)] (2), bridging boryl–borylene [(Cp*Ru)2(μ-CO){(μ3-BH(CH2S2)-κ2B:κ2S′:κ1S′′)}{Cr(CO)3}(μ3-BH)] (3), and sulfido bridged hetero-trimetallic complex [(Cp*Ru)2(μ-CO)3{Cr(CO)3}(μ3-S)] (4). In 2, one side of Ru2Cr-triangle features a μ3-BH ligand while the other side is quadruply bridged by a methanedithiolato ligand in an unsymmetrical fashion. Unlike 2, in complex 3, one side of the Ru2Cr-triangle has a μ3-BH ligand while the opposite side is bridged by a boryl ligand BH(CH2S2) in an unsymmetrical way (μ3–κ2:κ2:κ1) to the metal centers. Interestingly, when the similar reactions of arachno-1 were performed with heavier group-6 metal carbonyls [M(CO)5·THF] (M = Mo and W), it led to the formation of methanedithiolato bridged hetero-trimetallic chain complexes, [{Cp*Ru(CO)}2(μ-CO)2(μ3-CH2S2-κ2S′:κ2S′′){M(CO)2}] (5, M = Mo; 6, M = W) and sulfido-bridged hetero-trimetallic complexes [(Cp*Ru)2(μ-CO)3{M(CO)3}(μ3-S)] (7, M = Mo; 8, M = W), analogous to 4. In complexes 5 and 6, a Ru2M-chain is symmetrically bridged by a methanedithiolato ligand. On the other hand, in complexes 4, 7, and 8, a sulfido ligand coordinates to two ruthenium and one group-6 metal atoms in μ3-fashion. All the complexes have been characterized by 1H NMR, 13C NMR, UV-vis, IR spectroscopy, and mass spectrometry and their structural architectures have been unambiguously established by single crystal X-ray diffraction studies. In addition, theoretical investigations provided valuable insights into their electronic structures and bonding properties. [ABSTRACT FROM AUTHOR]

Transition metal triple‐decker complexes are an interesting class of sandwich complexes that engrossed great attention due to their structures and properties. Over the decades, synthesis of triple‐decker complexes featuring homocyclic, heterocyclic or π‐conjugated rings as middle decks have been abundantly reported. In this regard, the chemistry of such complexes bearing boron in the middle deck are well explored due to the ability of boron‐containing cycles to readily coordinate bifacially with metal atoms thereby forming triple‐decker complexes. On the other hand, electron counting rules and theoretical calculations have strengthened our knowledge of the structure and bonding in these complexes. Further, these complexes can be used as synthons to generate organometallic polymers having interesting electronic, optical and magnetic properties that can be appropriately tuned to cater to a wide range of applications. In our quest for novel metallaboranes and metallaheteroboranes, we have been successful in isolating various triple‐decker complexes that feature boron in the middle deck. This review explained elaborately the synthesis, structures, and bonding in such complexes reported by us and others. [ABSTRACT FROM AUTHOR]

Although Lipscomb predicted in 1977 that supra-icosahedral boron clusters would be viable, their synthesis has been impeded by the unavailability of appropriate synthetic methodologies. Herein, we report the first examples of the open 16-vertex oblato–hypho-titanaborane clusters [(Cp*Ti)2B14H17R] (1: R = H; 2: R = Me) having a non-Wadean 19-skeletal-electron-pair count. Interestingly, these clusters show a six-membered [Ti2B4] open face, which could lead to closo-19-vertex clusters. [ABSTRACT FROM AUTHOR]

Synthesis, bonding and chemistry of mono‐ and bimetallic complexes supported by chelating thiolato ligands have been established. Treatment of [Cp*VCl2]3 (1) with [LiBH4 ⋅ THF] followed by the addition of ethane‐1,2‐dithiol led to the formation of an EPR active bimetallic vanadium thiolato complex [(Cp*V){μ‐(SCH2CH2S)‐κ2S,S′)2{V(SCH2CH2S‐SH)}] (2). In complex 2, two ethane‐1,2‐dithiolato ligands are symmetrically coordinated to two vanadium atoms through μ‐S atoms. Interestingly, when similar reactions were carried out with heavier group 5 metal precursors, such as [Cp*NbCl4] (3 a), it afforded monometallic thiolato complex [Cp*Nb(SCH2CH2S)(SCH2CH2S−CH2S)] (4 a). On the other hand, the Ta‐analogue [Cp*TaCl4] (3 b) yielded thiolato species [Cp*Ta(SCH2CH2S)(SCH2CH2S−CH2S)] (4 b) and [Cp*Ta(SCH2CH2S) (SCH2CH2S−S)] (5). In complexes 4 a and 4 b, one ethane‐1,2‐dithiolato and one trithiolato ligand are coordinated to Nb and Ta centers, respectively. Whereas, in complex 5, one ethane‐1,2‐dithiolato and one 2‐disulfanylethanethiolato is coordinated to the Ta center. Moreover, the photolytic reaction of 5 with [Mo(CO)5 ⋅ THF] yielded heterobimetallic thiolato complex [(Cp*Ta){μ‐(SCH2CH2S)‐κ2S,S′}{μ‐(SCH2CH2S−CH2(CH3)S)κ2S′′ : κ1S‐′′′′ : κ1S′′′′′}{Mo(CO)3}] (6). All the complexes have been characterized by multinuclear NMR spectroscopy and single crystal X‐ray diffraction studies. Further, computational analyses were performed to provide an insight into the bonding of these complexes. [ABSTRACT FROM AUTHOR]

Isolation of planar [B6H6] is a long‐awaited goal in boron chemistry. Several attempts in the past to stabilize [B6H6] were unsuccessful due to the domination of polyhedral geometries. Herein, we report the synthesis of a triple‐decker sandwich complex of titanium [(Cp*Ti)2(μ‐η6 : η6‐B6H6)(μ‐H)6] (1), which features the first‐ever experimentally achieved nearly planar six‐membered [B6H6] ring, albeit within a [B6H12] borate. The small deviation from planarity is a direct consequence of the predicted structural pattern of the middle ring in 24 Valence Electron Count (VEC) triple‐decker complexes. The large ring size of [B6H6] in 1 brings the metal–metal distance into the bonding range. However, significant electron delocalization from the M−M bonding orbital to the bridging hydrogen and B−B skeleton in the middle decreases its bond strength. [ABSTRACT FROM AUTHOR]

Isolation of planar [B6H6] is a long‐awaited goal in boron chemistry. Several attempts in the past to stabilize [B6H6] were unsuccessful due to the domination of polyhedral geometries. Herein, we report the synthesis of a triple‐decker sandwich complex of titanium [(Cp*Ti)2(μ‐η6 : η6‐B6H6)(μ‐H)6] (1), which features the first‐ever experimentally achieved nearly planar six‐membered [B6H6] ring, albeit within a [B6H12] borate. The small deviation from planarity is a direct consequence of the predicted structural pattern of the middle ring in 24 Valence Electron Count (VEC) triple‐decker complexes. The large ring size of [B6H6] in 1 brings the metal–metal distance into the bonding range. However, significant electron delocalization from the M−M bonding orbital to the bridging hydrogen and B−B skeleton in the middle decreases its bond strength. [ABSTRACT FROM AUTHOR]

• Synthesis and structural characterization of tri-niobium cluster with a trithiaborate ligand. • Synthesis and structural characterization of three nido -ruthenium clusters. • Theoretical investigations have been performed to understand the electronic structure and bonding scenario in these clusters. In an effort to synthesize niobaheteroboranes and ruthenaheteroboranes, two different synthetic methods are developed. The reactions of [Cp*NbCl 4 ] (1) with chalcogenaborate ligands [LiBH 2 E 3 ] (E = S , Se) were carried out under reflux conditions. The reaction with sulfur yielded a triniobium polysulfide cluster [(Cp*Nb) 3 (μ 3 -S) 3 {B(OCH 3)}(μ -S) 3 ] (2) in which a trithiaborate ligand [S 3 B(OCH 3)]− is coordinated to Nb 3 framework in a cubane-type geometry. While the reaction with selenium generated a diniobium polyselenide cluster [(Cp*NbCl) 2 (μ -Se 2 -κ 1Se: κ 2Se') 2 (μ -O)] (3) in which two diselenide ligands {[Se 2 ]2−} are coordinated with both the metal centres in an unsymmetrical κ 1: κ 2 fashion. On the other hand, efforts were directed towards expliciting the coordinative sulfur centres of a preformed arachno ‑ruthenaborane [(Cp*Ru) 2 (B 3 H 8)(CS 2 H)] (arachno ‑ 4) , by carrying out the pyrolysis of arachno ‑ 4 with excess [BH 3 ⋅THF]. The reaction led to the formation of sulfido stabilized pileo cluster nido ‑ruthenathiaborane [2,3-(Cp*Ru) 2 (μ -H)(B 3 H 6)S] (5) , nido ‑ruthenaborane [2,3-(Cp*Ru) 2 (μ -H)(B 4 H 5 Me)] (6) and thiomethyl bridged nido ‑ruthenaborane [2,3-(Cp*Ru) 2 (μ -SMe)(B 3 H 6)] (7). One of the key features of complex 5 is the presence of an unusual pentacoordinated sulfido ligand(μ 5 -S). All the complexes have been characterized by multinuclear NMR, mass spectrometry and their structural architectures have been unambiguously established by single-crystal X-ray diffraction studies. In addition, theoretical investigations provided valuable insights into the electronic structures and bonding of these clusters. [ABSTRACT FROM AUTHOR]

A series of triborane and tetraborane analogues have been isolated and structurally characterized utilizing chalcogenatoborate ligands Li[BH3(EPh)] (E=S or Se). Thermolysis of [Cp*TaCl4] in the presence of Li[BH3(SPh)] afforded bimetallic tantallaheteroborane [(Cp*Ta)2(μ‐η3:η3‐B2H4S)(μ‐η2:η2‐SBH3)] (1) and hexasulfido trimetallic complex [(Cp*Ta)3(μ‐S)4(μ‐SPh)2] (2). Compound 1 is a fused ditantallaheteroborane, in which both di‐ and triborane analogues are stabilized by two tantalum atoms. In an attempt to synthesize the selenium analogues of 1 and 2, room‐temperature reaction of [Cp*TaCl4] with Li[BH3(SePh)] was carried out, which afforded bimetallic tantallaheteroborane [(Cp*Ta)2{μ‐η3:η3‐B3H6(SePh)}{μ‐SePh}2] (3), monometallic tantallaheteroboranes [Cp*Ta(SePh)2{B4H8‐n(SePh)n}] (4: n=0, 5: n=1), and trimetallic species [(Cp*Ta)3(μ‐Se)4{μ‐Se2(Se)}] (6). Compound 3 is the rarest example of triborane analogue {B3H6(SePh)} in the coordination sphere of two tantalum atoms. Whereas compounds 4 and 5 are examples of unsaturated metallaheteroboranes, in which the tetraborane analogues are stabilized in the coordination sphere of tantalum. One of the unique features of 3 and 5 is the presence of terminal B‐SePh. Compound 6 has similar Ta3Se6 trisbutterfly core as that of 2 with additional bridging selenide unit. All the compounds have been characterized by NMR spectroscopy, mass spectrometry, IR spectroscopy and single‐crystal X‐ray diffraction studies. [ABSTRACT FROM AUTHOR]

Despite the synthesis and structural characterization of closo‐hydroborate dianions, [BnHn]2− (n=6–12) more than 50 years ago, some ambiguity remains about the structure of [B8H8]2−. Although the solid‐state structure of [B8H8]2− was established by single‐crystal X‐ray studies in 1969, fast rearrangements in solution at accessible temperatures prevented its detailed characterization. We therefore stabilized a derivative of [B8H8]2− by using Cp2MBH3 and structurally characterized two new octaborane analogues, [(Cp2MBH3)2B8H6] (Cp=η5‐C5H5; M=Zr (1‐Zr) and Hf (1‐Hf)), so that the dynamics of the B8 skeleton were arrested. The solid‐state structures of both 1‐Zr and 1‐Hf comprise a dodecahedron core protected by {Cp2MBH3} moieties on both sides of the cluster. Spectroscopic characterization (11B NMR) validates the intactness of the B8 dodecahedron core in solution as well. Theoretical calculations establish that the two exo‐{Cp2MBH3} fragments provide structural and electronic structural stability to the B8 core and its intact dodecahedral dianionic nature. Furthermore, we propose isodesmic equations for the formation of higher analogues of the Bn core (n>8) guarded by different group 4 transition metals. Our analysis suggests that, as we move to higher polyhedra (n>10), the formation becomes unfavourable irrespective of metal. [ABSTRACT FROM AUTHOR]

In an effort to isolate the chalcogen-rich niobium analogue of [(Cp*Ta)3(μ-S)3(μ3-S)3BH], the room temperature reaction of [Cp*NbCl4] (Cp* = η5-C5Me5) with Li[BH2S3] was carried out. Although the objective of isolating the niobium analogue was not achieved, the reaction yielded a homocubane-type cluster [(Cp*Nb)3(μ-S)3(μ3-S)3(μ-S)BH], 1, and a hexa-sulfido cluster [(Cp*Nb)3(μ-S)6], 2. Cluster 1 is a notable example of a homocubane-type cluster in which one of the vertices of the homocubane is missing. Compound 1 may be considered as a hypo-electronic cluster with an electron count of 64 cve (cve = cluster valence electrons), whereas compound 2 shows the presence of two doubly bridging η1-S around each Nb–Nb bond. On the other hand, the room temperature reaction of [Cp*TaCl4] with selenaborate ligand, [LiBH2Se3], led to the formation of [(Cp*Ta)3(μ-Se)4{μ-Se2(Se2)}], 3. Compound 3 is one of the rarest examples having a Ta3Se6 core structure with a unique diselenide bridging fragment. The presence of a short Se–Se bond of this diselenide unit makes this molecule of further interest. All these compounds were characterized by 1H, 11B{1H} and 13C{1H} NMR spectroscopy, infrared spectroscopy, mass spectrometry, and single-crystal X-ray crystallography. Density functional theory (DFT) calculations were carried out to provide insight into the bonding and electronic structures of these chalcogen-rich trimetallic clusters. [ABSTRACT FROM AUTHOR]

Treatment of [Cp*TaCl SB 4 sb ] with chalcogen-ligated monoborate nucleophiles, [BH SB 3 sb (EPh)] SP - sp (E = S or Se) yielded various smaller borane analogues. Cover Feature: Metal Coordinated Tri- and Tetraborane Analogues (Eur. J. Inorg. Keywords: Boranes; Chalcogens; Metallaheteroboranes; Tantalum; Structure elucidation EN Boranes Chalcogens Metallaheteroboranes Tantalum Structure elucidation 4407 4407 1 11/24/21 20211122 NES 211122 B The Cover Feature b shows triborane and tetraborane analogues which are stabilized in the coordination sphere of tantalum atom(s). [Extracted from the article]

We have synthesized and structurally characterized two new borate complexes of early transition metals utilizing chalcogen based borate ligand Li[BH 3 (SPh)]. [Display omitted] • Two unique chalcogen stabilized borate complexes of Ta were isolated. • Complex 1 has two unique borate ligands, i.e., {BH 3 (SPh)} and {BH 3 (S)}. • Compound 2 has another unique borate ligand {BH 3 (C 6 H 4)S} and triborane analog. • The DFT calculations revealed the σ-donation of B-H bonds of borates to Ta atoms. In an attempt to isolate some electron precise early transition metal borate complexes, we have explored the reactions of [Cp*TaCl 4 ] (Cp* = η 5-C 5 Me 5) with chalcogen-based borate ligand Li[BH 3 (SPh)]. The room-temperature reaction yielded bimetallic borate complex [(Cp*Ta) 2 (μ -SPh){S(BH 3)}{SPh(BH 3)}] (1) that present two types of borate ligands, i.e., {BH 3 (SPh)} and {BH 3 (S)} ligands having unique coordination with the tantalum atoms. Interestingly, the {BH 3 (S)} ligand is coordinated to both the Ta centers in µ-η1:η2 fashion. On the other hand, thermolysis of [Cp*TaCl 4 ] in the presence of Li[BH 3 (SPh)] yielded a bimetallic borate species [(Cp*Ta) 2 (µ - η 3: η 3-B 2 H 4 S){ µ - η 2: η 2-S(C 6 H 4)BH 3 }] (2). Compound 2 contains a triborane analog and a borate ligand, which are coordinated to two Ta atoms. This can also be considered as a notable example of C H activated molecule, in which a B-C bond formation took place. Both the borate species have been characterized by mass spectrometry, IR spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction studies. The density functional theory (DFT) calculations further provided insights into the bonding and electronic structures of these bimetallic borate species. [ABSTRACT FROM AUTHOR]

• A series of binuclear thiolate complexes of group-5 metals have been synthesised and the role of metal and associated thiolate ligands influencing the structural and electronic properties of these complexes has been described. • The experimental results have been complemented and rationalized through DFT studies. The chemistry of group-5 transition metals, namely vanadium, niobium, and tantalum supported by thiolate ligand framework, has been described. Special emphasis has been given to the electronic and structural properties of binuclear thiolate complexes of group-5 metals exhibiting interesting coordination modes of the chelating thiolate ligands. The mild thermolysis of [(CH 2 S 2) 4 B]Na 5 with [Cp*VCl 2 ] 3 afforded the divanadium trithiocarbonate complex, [(Cp*V) 2 (μ-CS 3 -κ2S,S')(μ-H 2 CS 2 -κ2S'',S''')] (1) along with [{S(CH 2 S) 2 }VOCp*] (2). The single crystal X-ray structure of 1 illustrates that the trithiocarbonate and methanedithiolate ligands are symmetrically coordinated to two {Cp*V} units. However, reaction of the heavier group-5 metal precursor, [Cp*NbCl 4 ] with [(CH 2 S 2) 4 B]Na 5 at 60 °C in toluene produced a bimetallic trithiolate complex [(Cp*Nb) 2 (μ-SCS 2 -κ1S:κ3C,S',S'')(μ - S) 2 ] (3) along with [(Cp*Nb) 2 (μ,η2:η2-SH 3 B)(μ-S)(μ-H 2 CS 2 -κ2S,S')]. In a similar manner, [Cp*TaCl 4 ] led to the formation of ditantalum thiolate complexes [(Cp*Ta) 2 (μ-S)(μ-S 2 CH 2 CHS 2 -κ2S:κ2S',S'')(μ-H)(μ-S 2 CH 2 -κ2S''',S'''')] (4) and [Cl(Cp*Ta) 2 (μ-H)(μ-S 2 CH 2 -κ2S,S')(μ-S)(μ-S 2 CH 2 -κ2S'':κ1S''')] (5) along with [(Cp*Ta) 2 (μ-S){μ-(BH 2 S)(CH 2 S) 2 (BS 3)-κ2B:κ2S:κ4S',S'',S''',S''''}]. However, the reaction of LiBH 4 ·THF with [Cp*TaCl 4 ] followed by the thermolysis in the presence of S 2 C·PPh 3 led to the formation of [(Cp*Ta) 2 (μ-S)(μ-S 2 CH 2 -κ2S,S')(μ-H)(μ-CHS 3 -κ2S'':κ2S''',S'''')] (6) along with [(Cp*Ta) 2 (μ-S 2 CH 2 -κ2S,S') 2 (μ-H)(μ,η2:η2-B 2 H 5)] (I) and [(Cp*Ta) 2 (μ,η2:η2-B 2 H 6) 2 ] (II). Complex 3 is an example of trithiolate {CS 3 } stabilized bimetallic niobium complex. The (dimercaptomethyl)-methanedithiolate ligand (C 2 H 3 S 4) in 4 is coordinated to both the tantalum centres via three sulfur donors and displayed exclusive bonding mode (μ,κ 2 S:κ 2 S',S''). Complex 5 consists of two methanedithiolate ligands (S 2 CH 2) with different coordination towards the metal centres, whereas methanetrithiolate (HCS 3) and methanedithiolate (S 2 CH 2) units are symmetrically coordinated to both the tantalum centres in complex 6. This study demonstrates that the electronic properties of these complexes vary depending on the metal centres and thiolate ligands. This is reflected in the paramagnetic behaviour of the vanadium complex 1. In contrast, the niobium and tantalum thiolate complexes 3, 4, 5 and 6 are diamagnetic. Further, theoretical investigations provided the insights into the electronic structures and bonding of these group-5 metal thiolate complexes. [ABSTRACT FROM AUTHOR]