RESUMEN
Syntheses, structures, and electronic properties of group 5 metal-thiolate complexes that exhibit unusual coordination modes of thiolate ligands have been established. Room-temperature reaction of [Cp*VCl2]3 (Cp* = η5-C5Me5) with Na5[B(SCH2S)4] led to the formation of [Cp*VO{(SCH2)2S}] (1). The solid-state X-ray structure of 1 shows the formation of six-membered l,3,5-trithia-2-vanadacyclohexane that adopted a chair conformation. In a similar fashion, reactions of heavier group 5 precursors [Cp*MCl4] (M = Nb or Ta) with Na5[B(SCH2S)4] yielded bimetallic thiolate complexes [(Cp*M)2(µ-S){µ-C(H)S3-κ2S:κ2S',Sâ³}{µ-SC(H)S-κ2C:κ2Sâ´,S''''}] (3a: M = Nb and 3b: M = Ta). One of the key features of molecules 3a and 3b is the presence of square-pyramidal carbon, which is quite unusual. The reactions also yielded bimetallic methanedithiolate complexes [(Cp*Nb)2(µ-S)(µ-SCH2S-κ2S,S')(µ,η2:η2-BH3S)] (2) and [(Cp*Ta)2(µ-O)(µ-SCH2S-κ2S,S')(µ-H){µ-S2C(H)SCH2S-κ2Sâ³:κ2Sâ´,S''''}] (4). Complex 2 contains a methanedithiolate ligand that stabilizes the unsaturated niobaborane species. On the other hand, one ((mercaptomethyl)thio)methanedithiolate ligand {C2H4S3} is present in 4, which is coordinated to metal centers and exhibits the {µ-κ2Sâ³:κ2Sâ´,S''''} bonding mode. Along with the formation of 3b and 4, the reaction of [Cp*TaCl4] with Na5[B(SCH2S)4] yielded [(Cp*Ta)2(µ-S){µ-(SBS)S(CH2S)2(BH2S)-κ2B:κ2S:κ4S',Sâ³,Sâ´,S''''}] (5) containing a trithiaborate unit (BS3). Complex 5 consists of pentacoordinate boron that resides in a square-pyramidal environment. All the complexes have been characterized by multinuclear NMR, UV-vis spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies.
RESUMEN
The room-temperature reaction of [Cp*TaCl4 ] with LiBH4 â THF followed by addition of S2 CPPh3 results in pentahydridodiborate species [(Cp*Ta)2 (µ,η2 :η2 -B2 H5 )(µ-H)(κ2 ,µ-S2 CH2 )2 ] (1), a classical [B2 H5 ]- ion stabilized by the binuclear tantalum template. Theoretical studies and bonding analysis established that the unusual stability of [B2 H5 ]- 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)(CH2 S2 )}2 (B2 H5 )(H){M(CO)3 }] (6: M=Mo and 7: M=W), that retained the diborane(5) unit.
RESUMEN
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 inâ situ produced intermediate, generated from the low-temperature reaction of [Cp*WCl4 ] (Cp*=η5 -C5 Me5 ) and [LiBH4 â 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.
RESUMEN
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.
RESUMEN
The reaction of [CH{(CMe)(2,6-iPr2C6H3N)}2]GeCl with LiN(SiMe3)2 was previously reported, which led to the formation of a hetero-fulvene type germylene, [CH{(CMe)(C[double bond, length as m-dash]CH2)(2,6-iPr2C6H3N)}2]Ge through the deprotonation of the C-H bond from the methyl substituents. In this paper, we attempted the analogous reaction with (Dipp)NCMeCHCOMeGeCl using LiN(SiMe3)2 which gave rise to a metathesis product, (Dipp)NCMeCHCOMeGeN(SiMe3)2 (2). However, the reactions of 2 with [M2Cl2(µ-Cl)2(η5-Cp*)2] (M = Rh and Ir) resulted in cyclometallated Rh and Ir complexes through the activation of the C-H bond from the germylene ligand. The complexes were characterized by single crystal X-ray analysis, which authenticated the presence of Ge-Rh and Ge-Ir bonds. DFT studies have been performed to understand the mechanism.