A series of novel Cp*-based (Cp*=η(5)-C5Me5) agostic, bis(σ-borate), and boratrane complexes have been synthesized from diruthenium and dirhodium analogues of pentaborane(9). The synthesis and structural characterization of the first neutral ruthenadiborane(6) analogue are also reported. This new route offers a very efficient method for the isolation of bis(σ-borate) and agostic complexes from diruthenapentaborane(9).
The field of diborinane is sparsely explored area, and not many compounds are structurally characterized. The room-temperature reaction of [{Cp*RuCl(μ-Cl)}2] (Cp* = η5-C5Me5) with Na[BH3(SCHS)] yielded ruthenium dithioformato [{Cp*Ru(μ,η3-SCHS)}2], 1, and 1-thioformyl-2,6-tetrahydro-1,3,5-trithia-2,6-diborinane complex, [(Cp*Ru){(η2-SCHS)CH2S2(BH2)2}], 2. To investigate the reaction pathway for the formation of 2, we carried out the reaction of [(BH2)4(CH2S2)2], 3, with 1 that yielded compound 2. To the best of our knowledge, it appears that compound 2 is the first example of a ruthenium diborinane complex where the central six-membered ring [CB2S3] adopts the chair conformation. Furthermore, room temperature reaction of 1 with [BH3·thf] resulted in the isolation of agostic-bis(σ-borate) complex, [Cp*Ru(μ-H)2BH(S-CHS)], 4. Thermolysis of 4 with trace amount of tellurium powder led to formation of bis(bridging-boryl) complex, [{Cp*Ru(μ,η2-HBS2CH2)}2], 5, via dimerization of 4 followed by dehydrogenation. Compound 5 can be considered as a bis(bridging-boryl) species, in which the boryl units are connected to two ruthenium atoms. Theoretical studies and chemical bonding analyses demonstrate the reason for exceptional reactivity and stability of these complexes.
Reactions of the CS2 and CO2 heterocumulene ligands with nido-ruthenaborane cluster [1,2-(Cp*Ru)2(μ-H)2B3H7], 1, were explored (Cp* = pentamethylcyclopentadienyl). Compound 1 when treated with CS2 underwent metal-assisted hydroboration to yield arachno-ruthenaborane [(Cp*Ru)2(B3H8)(CS2H)], 2, with a dithioformato ligand attached to it. The chemistry of 2 was then explored with various transition metal carbonyl compounds under photolytic and thermolytic conditions. Thermolysis of 2 with [Mn2(CO)10] resulted in the formation of an unprecedented cubane-type cluster [(Cp*Ru)2Mn(CO)3(CS2H2)B3H4], 3, with a rare [M3E5] formulation (E = B, S). On the other hand, when compound 2 was photolyzed in the presence of [Mn2(CO)10], it yielded an incomplete cubane-type cluster [(Cp*Ru)2Mn(CO)3BH2(CS2H2)], 4. The room-temperature reaction of 2 with [Fe2(CO)9] yielded heterometallic arachno clusters [(Cp*Ru)(CO)2{Fe(CO)3}2S2CH3], 6 and [(Cp*Ru)2(B3H8)(CO){Fe(CO)3}2(CS2H)], 7. In contrast, photolysis of 2 with [Fe2(CO)9] yielded a tetrahedral cluster [(Cp*Ru)(CO)2S(μ-H){Fe(CO)3}3], 8, tethered to an exo-polyhedral moiety [(Cp*Ru)(CO)2]. Compound 6 provides an unusual bonding pattern by means of fusing the wing-tip vertex (S) of the [Fe2S2] butterfly core by an exo-polyhedral [(Cp*Ru)(CO)2] unit. Density functional theory calculations were carried out to provide insight into the mechanistic pathway, electronic structure, and bonding properties.
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.
A series of agostic σ-borane/borate complexes have been synthesized and structurally characterized from simple borane adducts. A room-temperature reaction of [Cp*Mo(CO)3 Me], 1 with Li[BH3 (EPh)] (Cp*=pentamethylcyclopentadienyl, E=S, Se, Te) yielded hydroborate complexes [Cp*Mo(CO)2 (μ-H)BH2 EPh] in good yields. With 2-mercapto-benzothiazole, an N,S-carbene-anchored σ-borate complex [Cp*Mo(CO)2 BH3 (1-benzothiazol-2-ylidene)] (5) was isolated. Further, a transmetalation of the B-agostic ruthenium complex [Cp*Ru(μ-H)BHL2 ] (6, L=C7 H4 NS2 ) with [Mn2 (CO)10 ] affords a new B-agostic complex, [Mn(CO)3 (μ-H)BHL2 ] (7) with the same structural motif in which the central metal is replaced by an isolobal and isoelectronic [Mn(CO)3 ] unit. Natural-bond-orbital analyses of 5-7 indicate significant delocalization of the electron density from the filled σBH orbital to the vacant metal orbital.
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