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Preparation and properties of dicyclopentadienylniobium(III) chloride
Cl4
Journal of Cb-ganomefallic Chemisby, 133 (1977) C14-Cl6 o EIlsevierSequoia S.A., Lausanne - hinted in The NetherlaMs
communication
Preliminary
PREF’ARATION AND PROPERTIES NIOBIUM(III) CHLORIDE
D._4. LEiLIENOVSKII*,
Loboratory
T.V. BAUKOVA
of Organo-Element
Moscow B234
OF DICSCLOPENTADIENYL-
and V-P_ FEDW
Compounds,
Chemical Department,
University of Moscow,
(U.S.S.R.)
(Recetved March 24th, 1977)
The preparation of an air-sensitive 164ectron complex, Cp,NbCl, is described. Its main property is easy transformation to 18-electron mononuclear compounds. CpIP&(=O)Cl and Cp2Nb(CO)Cl are obtained in oxidation and carbon monoxide gas addition processes, respectively. The physical properties of these complexes are described.
Results and discussion At present we have hardly any data on 164ectron niobocene derivatives, in contrast to the few, but well-known vanadium compounds of this kind [l--3]. Cp&bC1 was once mentioned to be a possible product of a reaction of C~,N~(X-C~H~) with HCL No properties of the compound were reported [4]_ A number of problems must first be resolved in the investigation of these electrondeficient complexes. Namely, we must know the reactivity as compared with corresponding complexes of adjacent elements, whether the structure is dimeric* or monomeric, and finally, the electron structure, since there may be two unpaired electrons in the molecule or none at all. In this paper we report the synthesis of the electron-deficient niobocene(III) chloride z+d some of its reactions. Ali experiments were performed in vacuum, or under argon using Schlenktype glassware. ESR spectra were recorded w%h a Vatian E-4 ESR spectrometer. ‘H NMR spectra were obtained with a V&an T-60 instrument. For the IR spectra investigation a Zeiss I-JR-20 machine was used. Good analyses were obtained for ah compounds. A very air-sensitive compound, Cp&IbCl, was prepared following a typical reduction method (eq. 1).
G33s)2PJb~
(1)
(dec. temp. 22O-222°C) Active metals such-as Na, Mg, Zn and Al in ether-type or aromatic solvents accomplish this process. The best method, however, is the action of sodium naph’thalene (NaphNa) in THF (eq. 2). (CSH5)2NbC12+ NaphNa + (CsHS)2NbCl
(2)
(58%) ._ In the course of the reduction reaction the strong ten-line ESR signal (g 1.9970; AM 116.5'G) of the initial Cp2NbClz f5] decreased and finally vanished almost completely, Cp2NbCl is a dark-brown complex readily soluble in the usual organic solvents, except for afkanes. Special measures had to be taken to eliminate traces of oxygen in solvents during the synthesis and work-up. Recently we carried out a reaction of n-C4HgLi with Cp2NbC12 [6,7]. In this reaction a trivalent transitory niobium complex, apparently of structure Li[Cp2Nb(C,H&l]~was formed before the complexes fmally isolated. In the present work we show that unstable Li[Cp2Nb(C,H,)Cl] is easily transformed to Cp,NbCl by the action of HCl in ether (eq. 3).. Lil(GH&Nb(CJ-IXI]
+ HCl
-LiCl,-C,H,, -----+
(C,H,),NbCl
(3)
The main feature in the chemical behaviour of Cp,NbCl is its fast transformation to l&electron complexes under the action of a suitable reagent. We investigated two processes (eq_ 4a, 4b).
t4a) (51%, dec. temp. > 190°C)
(56%, dec. temp. > 180°C) Reaction 4a is oxidation of niobium(lII) to niobium(V). The yield of the resulting oxoniobocene chloride is similar to that reported in previous papers [ 6,8]. The Nb=O stretching frequency is 867 cm-‘. The carbonylation reaction (like the oxidation) occurs instantaneously, even at 1 atm pressure of CO, and the monocarbonyl complex is the result. Carbonylniobocene chloride is a grey crystalline compound, soluble in benzene, toluene, THF, and insoluble in ether, alkanes, and alcohols. The stability of this complex in air is much higher than that of Cp,NbCl. The carbonylated chloride can easily be exposed to air for several days and only slow conversion to Cp,Nb(=O)Cl takes place. The CO stretching frequency is 1902 cm-‘. It is in good agreement with that of Cp,Nb(CO)H briefly described
Cl6
by Pa&all and Tebbe in 1971 f9]. The compound Cp2Nb(CO)C1 belongs to
the somewhat rarer trivalent, 18-ektion niobium complexes 19-141. Details concerning the structures of the compounds were obtained from the chemicaI reactions described above’and from the physical properties. The IR spectra of all compounds show absorption characteristics of nbonded cyclopentadienyl groups (absorption at 3100-3080,1430,1370, 1120,lOlO and 800 cm-‘) [15]. All compounds are diamagnetic and have no unpaired electrons on the niobium atom. Evidence for diamagnetism of Cp,NbCl in solution was obtained from the ESR spectra of the 10 -3-10-4 M solutions in various solvents. No signal associated with this compound was observed. Another proof is the uncomplicated PMR spectrum of Cp,NbCl. Parameters of PMR spectza (S, ppm, from internal TMS) of n-bcnded cyclopentadienyl.ligands in the niobocene complexes synthetised are as follows: C!p,NbC15.04 (acetone-&), CpJVb(=O)C16.42 (acetone-&), and Cp,Nb(CO)cL 4.88 (benzene-d,). References ad G.J_M_ -de= Kek, Rec. Trav. Cbim. Pars Bas, 80 (1961) 331. Liefde ~-peiier. ML J1 H_J. 2 D. Y’a J.S. Hsz?~er and J.H. Tcubez. J. ~omet%l. Chzn.. 74 (1974) 239. 3 Ei Bolllasn and J-EL Teuben. ;I. Orsznoaetal. Chem.. 110 (X976) 327. 4 F.W. Siege& ard E.J. Liefde Metier. Pmt. 4th Intern Conf. 0zganomeial. Chem. London. 1969. P. J-23. L.E. bfanzer. G.W. ParshaU and F.N. Tebbe. J. Amer. Chem. 5 LH_ Elson, J.IL Kochi. U. Iunde, sot.. 96 (1974) 7374. 6 D.A. Lemenovsk& T.V. Bat&ova. V.A. Knignikov. E.G. Perevalova. cad AX Nesneyanov. DoXady Akad. Naulr SSSR. 226 (1976) 585. 7 D.A. Lemenovskii. T.V. Baukova, E.G. Perevalova znd A.N. Nesxneyanov. izv. Akad. Nnu.k SSR. Ser. Khinx, (1976) 2404. 8 P.M. TreicheI and G.P. Wezber. J. Amer. Chem. Sot.. SO (1968) 1753. 9 F_N_ Tebbe arid G-W. PavfraDl J. Ames Chem. Sot. 93 (1911) 3793. W. Gusev. AA_ Pass&&E and Yu.T. Struchkov. Zh. Strukt. Khim.. 14 (1973) 868. 10 N.N. Kirillow, 11 W-A. Fowbs, L-S. Ru and D.A. Rice, 3. Orggometak Chem.. 54 (1973) C17. 12 C.R. Lucas and M.L.H. Green. J. Chem. Sot. Chem. Comnmn.. (1972) 1005. 13 F.N. Tebbe. J. Amer. Chem. Sac.. 96 (1973) 5412. 3.4 L.J. Guaxnberiler. P. Meakin and F.N. Tebbe. J. Am?r. Chen. Sot., 96 (1974) 5420. 1.5 F.A. Cotton and TJ. Marks. J. Amer. Chem_ Sot., 91(1969) 7281.
Journal of Cb-ganomefallic Chemisby, 133 (1977) C14-Cl6 o EIlsevierSequoia S.A., Lausanne - hinted in The NetherlaMs
communication
Preliminary
PREF’ARATION AND PROPERTIES NIOBIUM(III) CHLORIDE
D._4. LEiLIENOVSKII*,
Loboratory
T.V. BAUKOVA
of Organo-Element
Moscow B234
OF DICSCLOPENTADIENYL-
and V-P_ FEDW
Compounds,
Chemical Department,
University of Moscow,
(U.S.S.R.)
(Recetved March 24th, 1977)
The preparation of an air-sensitive 164ectron complex, Cp,NbCl, is described. Its main property is easy transformation to 18-electron mononuclear compounds. CpIP&(=O)Cl and Cp2Nb(CO)Cl are obtained in oxidation and carbon monoxide gas addition processes, respectively. The physical properties of these complexes are described.
Results and discussion At present we have hardly any data on 164ectron niobocene derivatives, in contrast to the few, but well-known vanadium compounds of this kind [l--3]. Cp&bC1 was once mentioned to be a possible product of a reaction of C~,N~(X-C~H~) with HCL No properties of the compound were reported [4]_ A number of problems must first be resolved in the investigation of these electrondeficient complexes. Namely, we must know the reactivity as compared with corresponding complexes of adjacent elements, whether the structure is dimeric* or monomeric, and finally, the electron structure, since there may be two unpaired electrons in the molecule or none at all. In this paper we report the synthesis of the electron-deficient niobocene(III) chloride z+d some of its reactions. Ali experiments were performed in vacuum, or under argon using Schlenktype glassware. ESR spectra were recorded w%h a Vatian E-4 ESR spectrometer. ‘H NMR spectra were obtained with a V&an T-60 instrument. For the IR spectra investigation a Zeiss I-JR-20 machine was used. Good analyses were obtained for ah compounds. A very air-sensitive compound, Cp&IbCl, was prepared following a typical reduction method (eq. 1).
G33s)2PJb~
(1)
(dec. temp. 22O-222°C) Active metals such-as Na, Mg, Zn and Al in ether-type or aromatic solvents accomplish this process. The best method, however, is the action of sodium naph’thalene (NaphNa) in THF (eq. 2). (CSH5)2NbC12+ NaphNa + (CsHS)2NbCl
(2)
(58%) ._ In the course of the reduction reaction the strong ten-line ESR signal (g 1.9970; AM 116.5'G) of the initial Cp2NbClz f5] decreased and finally vanished almost completely, Cp2NbCl is a dark-brown complex readily soluble in the usual organic solvents, except for afkanes. Special measures had to be taken to eliminate traces of oxygen in solvents during the synthesis and work-up. Recently we carried out a reaction of n-C4HgLi with Cp2NbC12 [6,7]. In this reaction a trivalent transitory niobium complex, apparently of structure Li[Cp2Nb(C,H&l]~was formed before the complexes fmally isolated. In the present work we show that unstable Li[Cp2Nb(C,H,)Cl] is easily transformed to Cp,NbCl by the action of HCl in ether (eq. 3).. Lil(GH&Nb(CJ-IXI]
+ HCl
-LiCl,-C,H,, -----+
(C,H,),NbCl
(3)
The main feature in the chemical behaviour of Cp,NbCl is its fast transformation to l&electron complexes under the action of a suitable reagent. We investigated two processes (eq_ 4a, 4b).
t4a) (51%, dec. temp. > 190°C)
(56%, dec. temp. > 180°C) Reaction 4a is oxidation of niobium(lII) to niobium(V). The yield of the resulting oxoniobocene chloride is similar to that reported in previous papers [ 6,8]. The Nb=O stretching frequency is 867 cm-‘. The carbonylation reaction (like the oxidation) occurs instantaneously, even at 1 atm pressure of CO, and the monocarbonyl complex is the result. Carbonylniobocene chloride is a grey crystalline compound, soluble in benzene, toluene, THF, and insoluble in ether, alkanes, and alcohols. The stability of this complex in air is much higher than that of Cp,NbCl. The carbonylated chloride can easily be exposed to air for several days and only slow conversion to Cp,Nb(=O)Cl takes place. The CO stretching frequency is 1902 cm-‘. It is in good agreement with that of Cp,Nb(CO)H briefly described
Cl6
by Pa&all and Tebbe in 1971 f9]. The compound Cp2Nb(CO)C1 belongs to
the somewhat rarer trivalent, 18-ektion niobium complexes 19-141. Details concerning the structures of the compounds were obtained from the chemicaI reactions described above’and from the physical properties. The IR spectra of all compounds show absorption characteristics of nbonded cyclopentadienyl groups (absorption at 3100-3080,1430,1370, 1120,lOlO and 800 cm-‘) [15]. All compounds are diamagnetic and have no unpaired electrons on the niobium atom. Evidence for diamagnetism of Cp,NbCl in solution was obtained from the ESR spectra of the 10 -3-10-4 M solutions in various solvents. No signal associated with this compound was observed. Another proof is the uncomplicated PMR spectrum of Cp,NbCl. Parameters of PMR spectza (S, ppm, from internal TMS) of n-bcnded cyclopentadienyl.ligands in the niobocene complexes synthetised are as follows: C!p,NbC15.04 (acetone-&), CpJVb(=O)C16.42 (acetone-&), and Cp,Nb(CO)cL 4.88 (benzene-d,). References ad G.J_M_ -de= Kek, Rec. Trav. Cbim. Pars Bas, 80 (1961) 331. Liefde ~-peiier. ML J1 H_J. 2 D. Y’a J.S. Hsz?~er and J.H. Tcubez. J. ~omet%l. Chzn.. 74 (1974) 239. 3 Ei Bolllasn and J-EL Teuben. ;I. Orsznoaetal. Chem.. 110 (X976) 327. 4 F.W. Siege& ard E.J. Liefde Metier. Pmt. 4th Intern Conf. 0zganomeial. Chem. London. 1969. P. J-23. L.E. bfanzer. G.W. ParshaU and F.N. Tebbe. J. Amer. Chem. 5 LH_ Elson, J.IL Kochi. U. Iunde, sot.. 96 (1974) 7374. 6 D.A. Lemenovsk& T.V. Bat&ova. V.A. Knignikov. E.G. Perevalova. cad AX Nesneyanov. DoXady Akad. Naulr SSSR. 226 (1976) 585. 7 D.A. Lemenovskii. T.V. Baukova, E.G. Perevalova znd A.N. Nesxneyanov. izv. Akad. Nnu.k SSR. Ser. Khinx, (1976) 2404. 8 P.M. TreicheI and G.P. Wezber. J. Amer. Chem. Sot.. SO (1968) 1753. 9 F_N_ Tebbe arid G-W. PavfraDl J. Ames Chem. Sot. 93 (1911) 3793. W. Gusev. AA_ Pass&&E and Yu.T. Struchkov. Zh. Strukt. Khim.. 14 (1973) 868. 10 N.N. Kirillow, 11 W-A. Fowbs, L-S. Ru and D.A. Rice, 3. Orggometak Chem.. 54 (1973) C17. 12 C.R. Lucas and M.L.H. Green. J. Chem. Sot. Chem. Comnmn.. (1972) 1005. 13 F.N. Tebbe. J. Amer. Chem. Sac.. 96 (1973) 5412. 3.4 L.J. Guaxnberiler. P. Meakin and F.N. Tebbe. J. Am?r. Chen. Sot., 96 (1974) 5420. 1.5 F.A. Cotton and TJ. Marks. J. Amer. Chem_ Sot., 91(1969) 7281.