Mikhail Galakhov

Construction of Heterometallic Cubanes [{Ti3Cp(μ3‐CMe)}(μ3‐O)3{Mo(CO)3}]

Incorporation of M(CO)(3) fragments by trinuclear Ti complexes [{Ti(3)Cp (µ(3)-CR)}(µ-O)(3)] and [{Ti(3)Cp (µ(3)-N)}(µ-NH)(3)] (Cp*=eta(5)-C(5)Me(5)) leads to the formation of an unprecedented class of heterometallic clusters with cubane structure [e.g., Eq. (a)]. Density functional calculations on these complexes indicate the existence of electron delocalization in the Ti(3)M cores (M=Cr, Mo, W).

Insertion of Isocyanide into Metal−Carbon Bonds of Alkylchloro(pentamethylcyclopentadienyl)niobium- and -tantalum Complexes − X-ray Structure of [TaCp*Cl2(CH2CMe2Ph){η2-C(CH2CMe2Ph)=N(2,6-Me2C6H3)}] and Unexpected Decomposition of Alkyldichloro(η2-iminoacyl) Complexes of Tantalum

Methylation of NbCp*Cl2Me2 using excess ZnMe2 gives NbCp*ClMe3 (1) which has been found to exhibit a Berry pseudorotation process on the NMR time scale (log A = 12.2 ± 0.3, Ea = 12.2 ± 0.4 kcal·mol−1, ΔH≠ = 11.6 ± 0.4 kcal·mol−1, ΔS≠ = −4.4 ± 1.3 e.u., ΔG≠298K = 12.9 kcal·mol−1). Alternatively, lithium dimethylamide reacts with NbCp*Cl2Me2 to form NbCp*Me2(NMe2)2 (2) which decomposes in solution under the elimination of methane to give the (dimethylamido)methylazaniobacyclopropane derivative NbCp*Me(NMe2)(η2-CH2NMe) (3). Reaction of NbCp*Cl2Me2 with 1 equiv. of 2,6-Me2C6H3NC results in a double methyl group migration to give the dichloroazaniobacyclopropane complex [NbCp*Cl2{η2-CMe2N(2,6-Me2C6H3)}] (4). Dialkyldichloro complexes TaCp*Cl2R2 [Cp* = η5-C5Me5; R = CH2SiMe3 (5), CH2CMe2Ph (6), CH2CMe3 (7), CH2C6H5 (8)] were obtained by treating TaCp*Cl4 with the requisite amounts of the appropriate alkylating agents. Reactions of the dialkyldichloro complexes TaCp*Cl2R2 (5−8) with 1 equiv. of 2,6-Me2C6H3NC resulted in migration of only one of the two alkyl groups to give (alkyl)dichloro(η2-iminoacyl) complexes [TaCp*Cl2R{η2-C(R)=NAr}] [Ar = 2,6-Me2C6H3; R = CH2SiMe3 (9), CH2CMe2Ph (10), CH2CMe3 (11), CH2C6H5 (12)]. The molecular structure of complex 10 has been determined by X-ray diffraction analysis. The η2-iminoacyl complexes 9−12 decompose in [D6]benzene or n-hexane solutions to give [TaCp*Cl2{N(2,6-Me2C6H3)}] and the corresponding trans or cis olefins R′−CH=CH−CH2−R′ [R′ = SiMe3 (9o), CMe2Ph (10o), CMe3 (11o), C6H5 (12o)]. A mechanism for this reaction is proposed. All the new compounds have been characterized by IR spectrophotometry, 1H- and 13C{1H}-NMR spectroscopy, and elemental analysis.

Fulvalene titanium and zirconium complexes: synthesis and NMR study of phosphanido-, alkyl-, and alkynyl-derivatives. X-ray crystal structures of [{Ti(η5−C5H5)(μ−PPH2)}2{μ−(η5−C5H4−η5−C5H4)}] and [{Zr(η5−C5H5)(μ−C≡CSiMe3)}2{μ−(η5−C5H4−η5−C5H4)}]

We gratefully acknowledge financial support from DGICYT (Project 92-0178-C) for this research. A.C. acknowledges MEC for a Fellowship.

Pentamethylcyclopentadienyl halo- and alkyl-alkoxo tantalum(V) complexes. Crystal structure of TaCp*(CH2SiMe3) 2{η2-O(2-CH2-6-MeC6H3)}

Abstract Reaction of TaCp∗Cl4 with MOR (M  Li, Na) in different molar ratios gives halo alkoxides TaCp ∗ Cl n ( OR ) 4−n (n = 3: R  t Bu 1 ; SiPh 3 2 ; 2,6- Me 2 C 6 H 3 3 ; n = 2: R = t Bu 4 ; SiPh 3 5 ; 2,6- Me 2 C 6 H 3 6 ; n = 1: R = SiMe 3 7 ) in good yields. The alkylidene complex TaCp∗(CH2SiMe3)2(CHSiMe3) is hydrolyzed in the presence of traces of water to give the oxo dialkyl derivative [TaCp∗(Ch2SiMe3)2O]n8, and reacts with 1 equivalent of 2,6-Me2C6H3NC affording a new η2-iminoacyl compound TaCp ∗ ( Ch 2 SiMe 3 ) CHSiME 3 ){η 2 - C(CH 2 Sime 3 ) N (2,6- Me 2 C 6 H 3 )} 9. Reactions of TaCP∗(CH2SiMe3)2(CHSiMe3) with 1 equivalent of C6H5OH and 4-MeC6H3(OH)2 result in the formation of the alkyl phenoxo TaCp∗(CH2SiMe3)3(OC6H5) 10 and 4-methyl pyrocatecholate TaCp∗(CH2SiMe3)2(O2C6H3Me) 11, whereas the relaxed reaction with 2,6-Me2C6H3OH leads to the cyclic alkyl-alkoxo compound TaCp ∗ ( CH 2 SiMe 3 ) 2 {η 2 - O (2- CH 2 -6- MeC 6 H 3 )]} 12. All the complexe were characterized by IR and NMR (1H and 13C) spectroscopy. The crystal and molecular structure of 12 has been determined. Crystals of 12 are triclinic, space group P 1 − with Z = 2 in a unit cell of dimensions a = 9.151(5) A , b = 11.835(5) A , c = 14.045(4) A , α = 89.35(3)°, β = 72.34(3)° and γ = 88.51(4)°, V = 1449(1) A 3 . Final values of R = 0.025 and Rw = 0.0655 were obtained from 5547 reflections measured (5070, > 2σ(1)).

Cyclopentadienyl dithiocarbamate and dithiophosphate molybdenum and tungsten complexes

Reactions of [MCp*Cl4 ]( MMo, W; Cp*h 5 -C5Me5) with salts of the N,N-diethyldithiocarbamate [Et2dtc] and O,O%-diethyldithiophosphate [Et2dtp] anions yield the paramagnetic metal(V) complexes [MCp*Cl3(Et2dtc)] (M Mo, W) and [MCp*Cl3(Et2dtp)] (MMo, W), respectively. Hydrolytic oxidation of both dithiocarbamate‐molybdenum complexes with aqueous hydrogen peroxide leads to h 2 -coordinated peroxo compounds [MoCp*Cl(O‐O)O], which were also obtained from [MoCp*Cl4]. The related complexes [MCp%Cl(O‐O)O] (M Mo, Cp%h 5 -C5H5 ;M W, Cp%h 5 -C5Me5) were isolated in a similar way. Reduction of a THF solution of [MoCp*Cl4] with one equivalent of 10% Na:Hg followed by the addition of one equivalent of ammonium dithiophosphate gives [MoCp*Cl2(Et2dtp)] which was also obtained via the reaction of [MoCp*Cl3(Et2dtp)] with MeMgCl, whereas reduction with three equivalents of Na:Hg in the presence of CN t Bu leads to the molybdenum(II) complex [MoCp*(Et2dtp)(CN t Bu)2] in high yield. All these compounds were characterized by elemental analysis, IR, 1 H- and 13 C-NMR spectroscopy, magnetic susceptibility measurements and the molecular structures of [Mo(h 5 -C5H5)Cl(O‐ O)O] and [Mo(h 5 ‐C5Me5)Cl3{h 2 -S2P(OEt)2}] were determined by X-ray diffraction studies.

Construction of Heterometallic Cubanes [{Ti3Cp*3(μ3‐CR)}(μ3‐O)3{Mo(CO)3}] (R=H, Me; Cp*=η5‐C5Me5) and [{Ti3Cp*3(μ3‐N)}(μ3‐NH)3{M(CO)3}] (M=Cr, Mo, W); Crystal Structure of [{Ti3Cp*3(μ3‐CMe)}(μ3‐O)3{Mo(CO)3}]

Der Einbau von M(CO)3-Fragmenten in die dreikernigen Ti-Komplexe [{Ti3Cp*3(μ3-CR)}(μ-O)3] und [{Ti3Cp*3(μ3-N)}(μ-NH)3] (Cp*=η5-C5Me5) fuhrt zu einer neuen Klasse von Heterometallclustern mit Cubanstruktur [z. B. Gl. (a)]. Dichtefunktionalrechungen deuten auf eine Elektronendelokalisierung in den Ti3M-Gerusten hin (M=Cr, Mo, W).

Half-sandwich dichloro, alkyl chloro, dialkyl, alkyl methyl and amido methyl imido cyclopentadienyl niobium and tantalum(V) complexes. Dynamic behaviour of amido imido tantalum derivatives

Abstract Reactions of NbCp′Cl 4 (Cp′=η 5 -C 5 H 4 SiMe 3 ) and TaCp*Cl 2 Me 2 (Cp*=η 5 -C 5 Me 5 ) with two equivalents of NHR 1 SiMe 3 and two equivalents of CNR 1 (M=Nb, R 1 =2,6-Me 2 C 6 H 3 ; 2,6- i Pr 2 C 6 H 3 ; SiMe 3 ; M=Ta, R 1 =2,6-Me 2 C 6 H 3 ), respectively, gave the dichloro imido derivatives [ MCpCl 2 ( NR 1 )] (M=Nb, Cp=Cp′, R 1 =2,6-Me 2 C 6 H 3 , 1 ; 2,6- i Pr 2 C 6 H 3 , 2 ; SiMe 3 , 3 ; M=Ta, Cp=Cp*, 4 ). Alkyl chloro imido complexes [ MCpClR ( NR 1 )], (R 1 =2,6-Me 2 C 6 H 3 ; M=Nb, Cp=Cp′, R=Me, 5 ; Cp*, 6 ; M=Ta, Cp=Cp*, R=Me, 7 ; NMe 2 , 8 ; O t Bu, 9 ) were obtained by treatment of dichloro derivatives 1 and 4 with the appropriate amount of alkylating reagent ( 5 , 7 one equivalent of ZnMe 2 ; 6 four equivalents of LiCp*; 8 , 9 one equivalent of LiR). When the same reaction was carried out with two equivalents of MgClMe ( 10 ) or LiR(RCH 2 SiMe 3 , 11 ; CH 2 CMe 3 , 12 ; NMe 2 , 13 ) and one equivalent of Mg(CH 2 C 6 H 5 ) 2 (THF) 2 ( 14 ) or Li 2 [ o -(NSiMe 3 ) 2 C 6 H 4 ] ( 15 ) the corresponding dialkyl imido derivatives [ MCpR 2 ( NR 1 )], (R 1 =2,6-Me 2 C 6 H 3 ; M=Nb, Cp=Cp′, R=Me, 10 ; CH 2 SiMe 3 , 11 ; CH 2 CMe 3 , 12 ; NMe 2 , 13 ; CH 2 C 6 H 5 , 14 ; M=Ta, CpCp*, R= o -(NSiMe 3 ) 2 C 6 H 4 , 15 ) can be prepared. The methyl complexes 5 , 7 reacted with one equivalent of LiR to give mixed alkyl methyl and amido methyl imido derivatives [ MCpMeR ( NR 1 )] (R 1 =2,6-Me 2 C 6 H 3 ; M=Nb, Cp=Cp′, R=CH 2 SiMe 3 , 16 ; NMe 2 , 17 ; M=Ta, Cp=Cp*, R=NMe 2 , 18 ; N i Pr 2 , 19 ; NH t Bu, 20 ). All the new complexes were characterized by usual IR and NMR spectroscopic methods. The rotation of 2,6-Me 2 C 6 H 3 ring and NR 2 (R=Me, i Pr) amido ligands around C ipso (aryl)–N imido and N amido –Ta bonds, respectively, were observed for complexes 8 , 18 and 19 and studied by 1 H-DNMR spectroscopy.

Synthesis of bis (tert-butyl)cyclopentadienyl derivatives of titanium and zirconium. NMR spectra and dynamic behaviour of the base-free [Zr(1,3-tBu2-η5-C5H3)(CH2Ph)2]+ cation

Financial support for this research by DGICYT (Project PB92-0178-C) is gratefully acknowledged. J.I.A. acknowledges Repsol Petroleo S.A. for a fellowship.

Neutral and cationic di(tert-butyl) cyclopentadienyl titanium, zirconium and hafnium complexes. Dynamic NMR study of the ligand-free cations [M(1,3-tBu2-η5-C5H3)(η5-f5H5)(CH3)]+(M=Zr, Hf)

Financial support for this research by DGICYT (Project PB92-0178C) is gratefully acknowledged. J.I.A. acknowledges Repsol Petroleo S.A. for a fellowship. A.M. is grateful to Consejeria Educaci6n (CAM) for a fellowship.

Alkyl chloro, dialkyl and mixed alkyl derivatives of imido(pentamethylcyclopentadienyl) tantalum(V). X-ray crystal structure of [TaCp*Cp′Cl{N(2,6-Me2C6H3)}], (Cp′=η5-C5H4SiMe3]

Abstract [TaCp*Cl2{N(2,6-Me2C6H3)}] (Cp*=η5-C5Me5) reacts with one equivalent of LiR (R=CH2SiMe3, CH2CMe2Ph, CH2CMe3, 2-(CH2NMe2)C6H4, C5H4SiMe3) or 0.5 equivalents of Mg(CH2C6H5)2(THF)2 to give the alkyl chloro complexes [TaCp*ClR{N(2,6-Me2C6H3)}],(R=CH2SiMe3, 1; CH2CMe2Ph, 2; CH2CMe3, 3; CH2C6H5, 4; 2-(CH2NMe2)C6H4, 5; C5H4SiMe3, 6). When the same reaction was carried out with two equivalents of lithium or one equivalent of magnesium reagent, the corresponding dialkyl derivatives [TaCp*R2{N(2,6-Me2C6H3)}],(R=CH2SiMe3, 7; CH2CMe2Ph, 8; C6H5, 9; CH2C6H5, 10; CH2CMe3, 11) were obtained. The mixed alkyl derivatives [TaCp*MeR{N(2,6-Me2C6H3)}], (R=CH2SiMe3, 12; CH2CMe2Ph, 13; C6H5, 14; CH2CMe3, 15; 2-(CH2NMe2)C6H4, 16; CH2C6H5, 17; C5H4SiMe3, 18) have been prepared by treatment of solutions containing [TaCp*ClMe{N(2,6-Me2C6H3)}] with one equivalent of lithium or 0.5 equivalents of magnesium reagent. All the new complexes were characterized by the usual IR and NMR spectroscopic methods. The crystal structure of 6 was determined by X-ray diffraction studies. Crystals of 6 are monoclinic, space group P21/c, with Z=4 in a unit cell of dimensions a=12.597(3), b=11.338(2), c=18.297(4) A and β=96.53(3)°. The structure was solved from diffractometer data by a combination of direct and Fourier methods and refined by full-matrix least squares fit on the basis of 4846 observed reflections to R1 and wR2 values of 0.0224 and 0.0574, respectively.