12793-14-5Relevant articles and documents
Synthesis and Reactivity of Bis(η-cyclopentadienyl) Trimethyltin derivatives of Niobium: Crystal and Molecular Structure of 2(μ-O)>
Green, Malcolm L. H.,Hughes, Andrew K.,Mountford, Philip
, p. 1407 - 1416 (1991)
The reaction between and LiBu followed by SnMe3Cl gives 2, also produced from and SnMe3H.Heating 2 with styrene, PMe3, isoprene or but-2-yne gives (L=η-H2C=CH-C6H5, 3; PMe3, 4; η-H2C=CHCMe=CH2, 5; or η-C2Me2, 6).Photolysis of complex 3 in the presence of CO, 2,6-Me2C6H3NC, MeCN, or PMe3 gives (L=CO, 7; 2,6-Me2C6H3NC, 8; η2-MeCN, 9a and 9b; or PMe3, 4).Heating 3 with H2 regenerates 2 and releases styrene.Compound 3, 5 or 6 reacts with SnMe3H to give the bis(stannyl) derivative 10, which is also formed by prolonged heating of with SnMe3H.Photolysis of 3 under CO2 gives a mixture of 7 and 2(μ-O)> 11 by cleavage of the CO2 molecule.Compound 11 crystallises in the orthorhombic space group Pbca with a=8.409(3), b=21.109(4) and c=15.582(3) Angstroem.The bridging oxygen atom sits on a crystallographic inversion centre giving a linear Nb-O-Nb group with Nb-O 1.9434(4) and Nb-Sn 2.8619(5) Angstroem.
Phosphinomethyl complexes of niobocene
Tueting, David R.,Olmstead, Marilyn M.,Schore, Neil E.
, p. 2235 - 2241 (1992)
Reaction of LiCH2P(C6H5)2 with Cp2NbCl2 gives paramagnetic Cp2Nb[CH2P(C6H5)2] 2 (1); Cp2Nb(Cl)CH2P(C6H5)2 (4) is observed only as an unstable intermediate. Oxidation of 1 by AgBF4 gives Cp2Nb[CH2P(C6H4)2] 2+BF4- (6); reduction by Na/C10H8 gives Na+{Cp2Nb[CH2P(C6H4) 2]2}- (5), both isolable in analytically pure form as stable, diamagnetic solids. The anion of the latter crystallizes as its Na(18-crown-6)(THF)2+ salt in the monoclinic space group C2/c with cell parameters a = 27.088 (15) ?, b = 9.560 (5) ?, c = 25.903 (14), β = 126.19 (3)°, and Z = 4. The structure was refined to R = 0.044 and Rw = 0.046 using 3493 uniquely observed reflections. Reaction of 1 with (C7H8)Mo(CO)4 gives Cp2Nb[μ-CH2P-(C6H5) 2]2Mo(CO)4 (7), which crystallizes in the monoclinic space group P21/n with cell parameters a = 13.401 (5) ?, b = 17.188 (5) ?, c = 19.768 (6), β = 99.25 (3)°, and Z = 4. The structure was refined to R = 0.081 and Rw = 0.085 using 1851 uniquely observed reflections. Both 5 and 7 possess pseudotetrahedral Nb atoms, the latter octahedral Mo. Both Nb and Na in 5 lie on crystallographic 2-fold axes; no interaction between Nb and P is evident. The C-Nb-C angles to the phosphinomethyl groups are found to be 74.2 (2)° in 5- (d2 Nb), ca. 80-85° in 1 (d1 Nb, estimated from ESR data), and 90.4° in 7 (d1 Nb).
The carbenoid nature of halophosphines. Carbene-like insertion mechanism in the reaction of chlorophosphines with Cp2NbH3
Nikonov, Georgii I.,Grishin, Yuri K.,Lemenovskii, Dmitry A.,Kazennova, Nadezhda B.,Kuzmina, Lyudmila G.,Howard, Judith A. K.
, p. 183 - 198 (2007/10/03)
We have studied the reactivity of Cp2NbH3 (1) with different chlorophosphines and showed that all the reactions occur at the niobium-hydride bond and proceed by two competitive routes, via the direct insertion of a chlorophosphine into the Nb-H bond and electron or/and hydride transfer mechanism. Reaction of 1 with the unhindered dialkyl-and diaryl-chlorophosphines C1PR2 (R = Et, Bu, Pri, Ph) gave the insertion product - the ionic complexes [Cp2NbH2(PHR2)]C1 (2) - in high yields. In contrast, reaction of 1 with the bulkier C1PBu12 proceeded much slower and resulted in the steady formation of Cp2NbC12 and HPBu12. Cp2NbC12 was also the product of the reactions of 1 with excess of C1P(OEt)2 and catecholechlorophosphite 7. The reaction of 1 with one equivalent of cyclic chlorodiaminophosphine C1P(N(CH3)2CH2-)2 (5) resulted in two competitive routes that led to the ionic complex [Cp2NbH2(HP(NR2)2)]C1 (2f) and molecular complex Cp2NbC1(HP(NR2)2) (6j). The reaction of 1 with two equivalents of cyclic 1-chloro-5,5-dimethyl-1-phospha-2,6-dioxahexane gave cationic diphosphite complex [Cp2Nb(PHR2)2]C1 (8) in high yield. This reactivity was explained in terms of the carbenoid nature of halophosphines due to the proposed relationship in the electronic structures of halophosphines and singlet methylene. Thus, reaction of 1 with the unhindered dialkyl-and diaryl-chlorophosphines proceeded by the direct insertion of a chlorophosphine C1PR2 into the Nb-H bond whereas with the more electron withdrawing substituents R at phosphorus the electron or/and hydride transfer mechanisms, leading to 6 and eventually to Cp2NbC12, could be operative. This concept also allowed us to explain the reactivity of chlorophosphines toward different unsaturated organic products. The facile syntheses of complexes Cp2Nb(PHR2)C1 (6) and Cp2Nb(PHR2)H (11) by the thermolysis and deprotonation of 2, respectively, was performed and the comparison with other methods was undertaken. Crystallographic studies of complexes 8 and Cp2Nb(PHPri2)Br are reported.
