Reactivity of Diruthenium and Dirhodium Analogues of Pentaborane(9): Agostic versus Boratrane Complexes

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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[(H B)bbza]), trihydro(2-aminobenzothiazolyl)borate (Na[(H B)abz]), and dihydrobis(2-mercaptopyridyl)borate (Na[(H B)mp ]) (bbza=bis(benzothiazol-2-yl)amine, abz=2-aminobenzothiazolyl, and mp=2-mercaptopyridyl). Photolysis of [Mn (CO) ] with Na[(H B)bbza] formed bis(σ)borate complex [Mn(CO) (μ-H) BHNCSC H (NR)] (1; R=NCSC H ). Octahedral complex [Re(CO) (N C S C H ) ] (2) was generated under similar reaction conditions with [Re (CO) ]. Similarly, when [Mn (CO) ] was treated with Na[(H B)abz], bis(σ)borate complex [Mn(CO) (μ-H) BH(HN CSC H )] (3) and the agostic complex [Mn(CO) (μ-H)BH(HN CSC H ) ] (4) were formed. To probe the potential formation of agostic complexes of the heavier group 7 metals, we carried out the photolysis of [M (CO) ] with Na[(H B)mp ] and found that [M(CO) (μ-H)BH(C H NS) ] (5: M=Re; 6: M=Mn) was formed in moderate yield. Complexes 1 and 3 feature a (κ -H,H,N) coordination mode, whereas 4, 5, and 6 display both (κ -H,N,N) and (κ -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) (BHNCSC H )(NR)(CO) PL L'] (R=NCSC H ; 7 a: L=L'=Ph; 7 b: L=Ph, L'=Me) and [Mn(μ-H) BHN(NCSC H )R(CO) PL L'] (R=NCSC H ; 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.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Saha

Ramalakshmi

Gomosta

et al. 2017

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“…The B⋅⋅⋅Ru bond distances of 2.697(4) in 4 and 2.736(4) Å in 5 are analogous to [Cp*Ru{κ 3 ‐H,S,S′‐H 2 B(bt) 2 }] (2.753(1) Å). However, the Ru⋅⋅⋅H−B bond distance of 1.692(2) Å and 1.755(3) Å for 4 and 5 are shorter as compared to [Cp*Ru{κ 3 ‐H,S,S′‐H 2 B(bt) 2 }] 1.830(3) Å …”

Section: Resultsmentioning

confidence: 99%

Reactivity of [M₂(μ‐Cl)₂(cod)₂] (M=Ir, Rh) and [Ru(Cl)₂(cod)(CH₃CN)₂] with Na[H₂B(bt)₂]: Formation of Agostic versus Borate Complexes

Bakthavachalam

Yuvaraj

Zafar

et al. 2016

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Treatment of [M (μ-Cl) (cod) ] (M=Ir and Rh) with Na[H B(bt) ] (cod=1,5-cyclooctadiene and bt=2-mercaptobenzothiazolyl) at low temperature led to the formation of dimetallaheterocycles [(Mcod) (bt) ], 1 and 2 (1: M=Ir and 2: M=Rh) and a borate complex [Rh(cod){κ -S,S'-H B(bt) }], 3. Compounds 1 and 2 are structurally characterized metal analogues of 1,5-cyclooctadiene. Metal-metal bond distances of 3.6195(9) Å in 1 and 3.6749(9) Å in 2 are too long to consider as bonding. In an attempt to generate the Ru analogue of 1 and 2, that is [(Rucod) (bt) ], we have carried out the reaction of [Ru(Cl) (cod)(CH CN) ] with Na[H B(bt) ]. Interestingly, the reaction yielded agostic complexes [Ru(cod)L{κ -H,S,S'-H B(bt) }], 4 and 5 (4: L=Cl; 5: L=C H NS ). One of the key differences between 4 and 5 is the presence of different ancillary ligands at the metal center. The natural bond orbital (NBO) analysis of 1 and 2 shows that there is four lone pairs of electrons on each metal center with a significant amount of d character. Furthermore, the electronic structures and the bonding of these complexes have been established on the ground of quantum-chemical calculations. All of the new compounds were characterized by IR, H, B, C NMR spectroscopy, and X-ray crystallographic analysis.

“…Our group has also been actively involved in the synthesis of electron‐precise transition‐metal–boron complexes, especially from metallaborane species . This has led to the isolation of several triply‐bridged trimetallic borylene, boryl, diborane, and B‐agostic complexes . In an effort to find efficient methods for the preparation of such complexes, we used different synthetic precursors.…”

Section: Introductionmentioning

confidence: 99%

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

Saha

Ramalakshmi

Borthakur

et al. 2017

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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 ] as precursors (L'=η -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*=η -C Me ). For example, treatment of Na[(H B)bbza] or Na[(H B)mp ] (bbza=bis(benzothiazol-2-yl)amine; mp=2-mercaptopyridyl) with [L'M(μ-Cl)Cl ] yielded [(η -p-cymene)RuBH{(NCSC H )(NR)} ] (2; R=NCSC H ), [{N(NCSC H ) }RhBH{(NCSC H )(NR)} ] (3; R=NCS-C H ), [(η -p-cymene)RuBH(L) ] (5; L=C H NS), and [Cp*MBH(L) ] (6 and 7; L=C H NS, M=Ir or Rh). In order to delineate the significance of the ligands, we studied the reactivity of [(COD)Rh(μ-Cl)] with Na[(H B)bbza], which led to the formation of the isomeric agostic complexes [(η -COD)Rh(μ-H)BHRh(C H N S ) ], 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.