Synthesis and characterization of the octahydrotriborate complexes Cp*V(B3H8)2 and Cp*Cr(B3H8)2 and the unusual cobaltaborane cluster Cp*2Co2(B6H14)

The new compounds CpV(B(3)H(8))(2), CpCr(B(3)H(8))(2), and Cp(2)Co(2)(B(6)H(14)) have been synthesized by treating the pentamethylcyclopentadienyl complexes [CpVCl(2)](3), [CpCrCl(2)](2), and [CpCoCl](2) with NaB(3)H(8). X-ray crystallography shows that CpV(B(3)H(8))(2) and CpCr(B(3)H(8))(2) have the same ligand sets but different molecular structures: the vanadium compound contains two bidentate B(3)H(8) ligands (i.e., bound to the metal center via two vicinal hydrogen atoms), whereas the chromium compound has one bidentate B(3)H(8) ligand and one B(3)H(8) ligand bound in an unprecedented fashion via two geminal hydrogen atoms. The "gem-bound" B(3)H(8) group itself has an atypical structure consisting of a BH(2)-BH(2)-BH(3) triangle with one additional hydrogen atom bridging the unique BH(2)-BH(2) edge. The B-B distances are nearly identical within experimental error at 1.790(5), 1.792(5), and 1.786(6) Angstrom. The relationship between the electronic and molecular structures of the V and Cr compounds is briefly discussed. The structure of Cp(2)Co(2)(B(6)H(14)) can be viewed in two different ways: as a dicobalt complex in which two CpCo units are each bound to four adjacent boron atoms of an S-shaped B(6)H(14) ligand, or as an eight-vertex hypho cluster compound. In the former case, the B(6)H(14) ligand is best regarded as a dianionic bi-borallyl group H(3)B(mu-H)BH(mu-H)BHBH(mu-H)BH(mu-H)BH(3) in which one hydrogen at each end of the chain is involved in an agostic interaction. From a cluster point of view, the structure of Cp(2)Co(2)(B(6)H(14)) can be generated by removing three adjacent high-connectivity vertices from the eleven-vertex closo polyhedron. The Co-B distances vary from 2.008(5) to 2.183(4) Angstrom, and the B-B distances within in the S-shaped chain range from 1.734(8) to 1.889(6) Angstrom. Finally, a new synthesis of the known molybdenum compound Cp(2)Mo(2)(B(5)H(9)) is described; its structure as established by X-ray crystallography closely resembles that of the previously described (C(5)H(4)Me) analogue.     

Condensed tantalaborane clusters: synthesis and structures of [(Cp*Ta)2B5H7{Fe(CO)3}2] and [(Cp*Ta)2B5H9{Fe(CO)3}4

The reaction of [(Cp*Ta)(2)B(4)H(9)(μ-BH(4))] (1; Cp* = η(5)-C(5)Me(5)) with [Fe(2)(CO)(9)] in hexane yielded [(Cp*Ta)(2)B(5)H(7){Fe(CO)(3)}(2)] (2) and [(Cp*Ta)(2)B(5)H(9){Fe(CO)(3)}(4)] (3) in moderate yield. Cluster 2 represents the first example of a bicapped pentagonal-bipyramidal metallaborane with a deformed equatorial plane, and 3 can be described as a fused cluster in which two pentagonal-bipyramidal units are fused through a common 3-vertex triangular face. Compounds 2 and 3 have been characterized by mass spectrometry and IR, (1)H, (11)B, and (13)C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis.     

Synthesis,Structure, Bonding,and Reactivity of Metal Complexes Comprising Diborane(4) and Diborene(2): [{Cp*Mo(CO)2}2{μ‐η2:η2‐B2H4}] and [{Cp*M(CO)2}2B2H2M(CO)4], M=Mo,W

The reaction of [(Cp*Mo)₂(μ‐Cl)₂B₂H₆] ( 1 ) with CO at room temperature led to the formation of the highly fluxional species [{Cp*Mo(CO)₂}₂{μ‐η²:η²‐B₂H₄}] ( 2 ). Compound 2, to the best of our knowledge, is the first example of a bimetallic diborane(4) conforming to a singly bridged C_s structure. Theoretical studies show that 2 mimics the Cotton dimolybdenum–alkyne complex [{CpMo(CO)₂}₂C₂H₂]. In an attempt to replace two hydrogen atoms of diborane(4) in 2 with a 2e [W(CO)₄] fragment, [{Cp*Mo(CO)₂}₂ B₂H₂W(CO)₄] ( 3 ) was isolated upon treatment with [W(CO)₅?thf]. Compound 3 shows the intriguing presence of [B₂H₂] with a short B?B length of 1.624(4) Å. We isolated the tungsten analogues of 3 , [{Cp*W(CO)₂}₂B₂H₂W(CO)₄] ( 4 ) and [{Cp*W(CO)₂}₂B₂H₂Mo(CO)₄] ( 5 ), which provided direct proof of the existence of the tungsten analogue of 2 .     

Synthesis,Structure, Bonding,and Reactivity of Metal Complexes Comprising Diborane(4) and Diborene(2): [{Cp*Mo(CO)2}2{μ‐η2:η2‐B2H4}] and [{Cp*M(CO)2}2B2H2M(CO)4], M=Mo,W

The reaction of [(Cp*Mo)₂(μ‐Cl)₂B₂H₆] ( 1 ) with CO at room temperature led to the formation of the highly fluxional species [{Cp*Mo(CO)₂}₂{μ‐η²:η²‐B₂H₄}] ( 2 ). Compound 2, to the best of our knowledge, is the first example of a bimetallic diborane(4) conforming to a singly bridged C_s structure. Theoretical studies show that 2 mimics the Cotton dimolybdenum–alkyne complex [{CpMo(CO)₂}₂C₂H₂]. In an attempt to replace two hydrogen atoms of diborane(4) in 2 with a 2e [W(CO)₄] fragment, [{Cp*Mo(CO)₂}₂ B₂H₂W(CO)₄] ( 3 ) was isolated upon treatment with [W(CO)₅⋅thf]. Compound 3 shows the intriguing presence of [B₂H₂] with a short B−B length of 1.624(4) Å. We isolated the tungsten analogues of 3 , [{Cp*W(CO)₂}₂B₂H₂W(CO)₄] ( 4 ) and [{Cp*W(CO)₂}₂B₂H₂Mo(CO)₄] ( 5 ), which provided direct proof of the existence of the tungsten analogue of 2 .     

Reaction of a ruthenium B-carboranyl hydride complex and BH3(SMe2): Selective formation of a pincer-supported metallaborane LRu(B3H8)

Reaction of a boryl hydride pincer complex (POBOP)Ru(H)(PPh₃) (POBOP?=?1,7-OP(i-Pr)₂-m-2-carboranyl) and BH₃(SMe₂) at 70?°C led to the selective formation of a pincer-supported metallaborane (POBOP)Ru(B₃H₈). Single crystal structure of (POBOP)Ru(B₃H₈) was determined. This complex features coordination of the carborane cluster through adjacent boryl and borane groups that impose significantly different trans-influence on the coordinated B₃H₈ fragment.     

Nitrosyl Complexes 6.Reactions of Na[Fe(CO)_3NO]with Cp~*M(CO)_3Cl(Cp~*=η~5-CH_3C_5H_4,M=Mo or W):Crystal structures of Cp~*M(CO)_2NO and Cp~*M(μ_3-NH)(μ_2-NO)(μ_2-CO)Fe_2(CO)_6

Sodium nitrosylcarbonyliron reacts with methylcyclopentadienylcarbonylmetal(Mo orW)chloride in CH_3OH/THF at room temperature to give CpMo(CO)_2NO(1a)(Cp=η~5-CH_3C_5H_4)or CpW(CO)_2NO(1b),[CpMo(CO)_3]_2(2a)or[CpW(CO)_3]_2(2b),and CpMo(μ3-NH)(μ2-NO)-(μ2-CO)Fe_2(CO)_6(3a)or CpW(μ3-NH)(μ2-NO)(μ2-CO)Fe_2(CO)_6(3b),respectively.Complexes1a,1b,3a and 3b were analyzed by IR,NMR,MS and elemental analyses,and the crystalstructures of 1b,3a and 3b were determined by X-ray diffraction method.The new clusters 3aand 3b have μ3-NH ligands which were formed by redaction of NO in the synthetic reactions.     

Formation of Isomeric Tetrathiotungstate Clusters [{Cp*Ru(CO)}2(WS4){W(CO)4}] by the Reaction of [Cp*2Ru2S4] with [W(CO)3(MeCN)3]

Thermal and photochemical interconversion occurs between the isomeric pair of tetrathiotungstate [WS₄]²⁻ clusters 1 and 2 , which were formed by thermolysis of [Cp^*₂Ru₂S₄] and [W(CO)₃(MeCN)₃] [Eq. (1)] and then structurally characterized. During synthesis, a dramatic redistribution of ligands between the Ru and W atoms takes place without the loss of any CO and S ligands.     

A new reaction of [Cp((CO)2Fe(PPh2H)]PF6 with NaBH4 to give Cp(CO)(H)Fe(PPh2H) via Cp(CO)2FeH and PPh2H

[Cp((CO)₂Fe(PPh₂H)]PF₆ reacts with NaBH₄ to give the intermediates CpFe(CO)₂H and PPh₂H, which are then converted into Cp(CO)(H)Fe(PPh₂H). [Cp(CO)₂FeL]PF₆ (L = P(OMe)₃, P(OEt)₃ and P(OⁱPr)₃) reacts with NaBH₄ to give the product Cp(CO)(H)FeL directly without Cp(CO)₂FeH and L even being formed transiently. The proposed reaction mechanism is that H⁻ attacks th phosphorus atom to give a metallaphosphorane complex, followed by coupling between a Cp(CO)₂Fe fragment and H on the hypervalent phosphorus.     

Complexes of decamethylsilicocene: Cp2*Si(CO) and Cp2*Si(N2)

The synthesis and IR spectroscopic detection of the monocarbonyl and mononitrogen complex of decamethylsilicocen in liquid xenon (LXe) and liquid nitrogen (LN₂) is reported. The reactions were found to be highly incomplete under a few bar of CO or N₂ and reversibel when the pressure is released. Cp₂*Si(CO) is characterized by three isotopomeres and Cp₂*Si(N₂) was synthesized on two independent routes.     

Reaktionen von Cyclostibanen (RSb)n [R = (Me3Si)2CH,n = 3; Me3CCH2, n = 4, 5] mit den Übergangsmetallcarbonyl‐Komplexen [W(CO)5(thf)], [CpxMn(CO)2(thf)], [CpxCr(CO)3]2 und [Co2(CO)8]; Cpx = MeC5H4

Reactions of Cyclostibanes, (RSb)_n [R = (Me₃Si)₂CH, n = 3; Me₃CCH₂, n = 4, 5] with the Transition Metal Carbonyl Complexes [W(CO)₅(thf)], [Cp^xMn(CO)₂(thf)], [Cp^xCr(CO)₃]₂, and [Co₂(CO)₈]; Cp^x = MeC₅H₄ (RSb)₃ [R = (Me₃Si)₂CH] reacts with [W(CO)₅(thf)], [Cp^xMn(CO)₂(thf)], or [Co₂(CO)₈] to give [(RSb)₃W(CO)₅] ( 1 ), [RSb{Mn(CO)₂Cp^x}₂] ( 2 ) or [RSbCo(CO)₃]₂ ( 3 ). The reaction of (R′Sb)_n (n = 4, 5; R′ = Me₃CCH₂) with [Cp^xCr(CO)₃]₂ leads to [(R′Sb)₄{Cr(CO)₂Cp^x}₂] ( 4 ); Cp^x = MeC₅H₄, thf = Tetrahydrofuran.     

[Co4P2(PtBu2)2(CO)8] und [{Co(CO)3}2P4tBu4] aus Co2(CO)8 und tBu2P–P=P(Me)tBu2

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XIX. [Co₄P₂(P^tBu₂)₂(CO)₈] and [{Co(CO)₃}₂P₄^tBu₄] from Co₂(CO)₈ and ^tBu₂P–P=P(Me)^tBu₂ Co₂(CO)₈ reacts with ^tBu₂P–P=P(Me)^tBu₂ yielding the compounds [Co₄P₂(P^tBu₂)₂(CO)₈] ( 1 ) and [{η^2tBu₂P=P–P=P^tBu₂}{Co(CO)₃}₂] ( 2 a ) cis, ( 2 b ) trans. In 1 , four Co and two P atoms form a tetragonal bipyramid, in which two adjacent Co atoms are μ₂‐bridged by ^tBu₂P groups. Additionally, two CO groups are linked to each Co atom. In 2 a and 2 b , each of the Co(CO)₃ units is η²‐coordinated to the terminal P₂ units resulting in the cis‐ and trans‐configurations 2 a and 2 b . 1 crystallizes in the orthorhombic space group Pnnm (No. 58) with a = 879,41(5), b = 1199,11(8), c = 1773,65(11) pm. 2 a crystallizes in the monoclinic space group P2₁/n (No. 14) with a = 875,97(5), b = 1625,36(11), c = 2117,86(12) pm, β = 91,714(7)°. 2 b crystallizes in the triclinic space group P 1 (No. 2) with a = 812,00(10), b = 843,40(10), c = 1179,3(2) pm, α = 100,92(2)°, β = 102,31(2)°, γ = 102,25(2)°.     

Dynamic electron transfers in B2H6 and Cu(PH3)2(BH4)

In order to investigate the coupling of molecular vibrations and electron distribution, dynamic electron transfers in B₂H₆ and Cu(PH₃)₂(BH₄) are lated by using a new variational method. In both molecules, the dynamic electron density near bridging hydrogen atoms decreases to form the density valley by exciting specific vibrational modes. On the other hand, in both sides of the valley density hills grow up. For these molecules, similar contour maps are given by the modes with different symmetry which have large contribution of the bridging ligands. While the dynamic electron transfer of B₂H₆ arises in symmetric form, the vibrational modes of the Cu complex gives the asymmetric redistribution of the dynamic electron density. This is attributed to the difference of the symmetry between the two molecules.     

Structural chemistry of "defect" cyanometalate boxes: (Cs subset [CpCo(CN)3]4[Cp*Ru]3) and (M subset [Cp*Rh(CN)3]4[Cp*Ru]3) (M = NH4, Cs)

A series of heptametallic cyanide cages are described; they represent soluble analogues of defect-containing cyanometalate solid-state polymers. Reaction of 0.75 equiv of [Cp*Ru(NCMe)3]PF6, Et(4)N[Cp*Rh(CN)3], and 0.25 equiv of CsOTf in MeCN solution produced (Cs subset [CpCo(CN)3]4[Cp*Ru]3)(Cs subset Rh4Ru3). 1H and 133Cs NMR measurements show that Cs subset Rh4Ru3 exists as a single Cs isomer. In contrast, (Cs subset [CpCo(CN)3]4[Cp*Ru]3) (Cs subset Co4Ru3), previously lacking crystallographic characterization, adopts both Cs isomers in solution. In situ ESI-MS studies on the synthesis of Cs subset Rh4Ru3 revealed two Cs-containing intermediates, Cs subset Rh2Ru2+ (1239 m/z) and Cs subset Rh3Ru3+ (1791 m/z), which underscore the participation of Cs+ in the mechanism of cage formation. 133Cs NMR shifts for the cages correlated with the number of CN groups bound to Cs+: Cs subset Co4Ru4+ (delta 1 vs delta 34 for CsOTf), Cs subset Rh4Ru3 where Cs+ is surrounded by ten CN ligands (delta 91), Cs subset Co4Ru3, which consists of isomers with 11 and 10 pi-bonded CNs (delta 42 and delta 89, respectively). Although (K subset [Cp*Rh(CN)3]4[Cp*Ru]3) could not be prepared, (NH4 subset [Cp*Rh(CN)3]4[Cp*Ru]3) (NH4 subset Rh4Ru3) forms readily by NH4+-template cage assembly. IR and NMR measurements indicate that NH4+ binding is weak and that the site symmetry is low. CsOTf quantitatively and rapidly converts NH4 subset Rh4Ru3 into Cs subset Rh4Ru3, demonstrating the kinetic advantages of the M7 cages as ion receptors. Crystallographic characterization of CsCo4Ru3 revealed that it crystallizes in the Cs-(exo)1(endo)2 isomer. In addition to the nine mu-CN ligands, two CN(t) ligands are pi-bonded to Cs+. M subset Rh4Ru3 (M = NH4, Cs) crystallizes as the second Cs isomer, that is, (exo)2(endo)1, wherein only one CN(t) ligand interacts with the included cation. The distorted framework of NH4 subset Rh4Ru3 reflects the smaller ionic radius of NH4+. The protons of NH4+ were located crystallographically, allowing precise determination of the novel NH4...CN interaction. A competition experiment between calix[4]arene-bis(benzocrown-6) and NH4 subset Rh4Ru3 reveals NH4 subset Rh4Ru3 has a higher affinity for cesium.