METALLOCENE DERIVATIVES OF EARLY TRANSITION METALS. PART 2. SUBSTITUTED CYCLOPENTADIENYL GROUP 4A DICHLORO-METALLOCENE COMPLEXES (M=Zr OR Hf; R=Me, Et, Pri, But, OR SiMe3), THEIR MONO- AND DI-ALKYL DERIVATIVES (X=Cl OR R';R'= CH2SiMe3 OR CH2CME3...

DOI: 10.1039/DT9810000805

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 805 - 813 (1981)

Update date:2022-08-05

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Authors:

Lappert, Michael F.

Pickett, Christopher J.

Riely, Paul I.

Yarrow, Paul I. W.

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Article abstract of DOI:10.1039/DT9810000805

The substituted d⁰ metallocene dichloro-complexes 2 (M = Ti^IV, Zr^IV, or Hf^IV; R = Me, Et, Prⁱ, Bu^t, or SiMe3), (1)-(11), have been prepared from MCl4 and 2Li in tetrahydrofuran (thf).From the appropriate dichloride and either(i) MgR'Cl in CH2Cl2 there was obtained the chloro(alkyl) (R = CH2SiMe3) or , or (ii) akyl-lithium in OEt2 the dialkyl (M'= Zr or Hf; R'' = H, Me, Et, Prⁱ or Bu^t; X = C or Si), (13)-(16), was produced; treatment of t)2Cl2> with BBr3 in CH2Cl2 gave t)2Br2>.The 1H n.m.r. spectra of each of the dichlorides (1)-(11) show the ring protons of the C5H4R group as an AA'BB' or A2B2 (R = SiMe3) signal; the dialkyls (13)-(16) show this feature as an A2X2 pattern, whereas in t)2SiMe3)Cl> it appears as ABCD.The 13C n.m.r. spectra show three signals for the corresponding carbon atoms (C5H4R) and the chemical shift data are compared with results on substituted ferrocenes or benzenes, or C6H5R.Treatment of the complex with an equimolar portion of Na in thf at 20 deg C yields an appropriate d¹ dialkylmetal(III) complex, which is persistent for M = Ti or Zr but not for M = Hf, and is characterised by its e.s.r. spectrum av., 1.984-1.993; a(1H), 0.175-0.360 mT; a(^47/49Ti), 0.720-1.05. mT;a(⁹¹Zr),1.000-2.410 mT> showing coupling with the α protons of the alkyl group R'.As each of these (Zr) dialkyls undergoes irreversible one-electron reduction at a Pt electrode in 0.2 mol dm^-3 in thf the above d¹ complexes are formulated as .Cyclic voltammetry data are provided for several metallocene(IV) complexes: (i) dichlorides ^-(M = Zr), and E_1/2^red is nearly 1 V more negative than for Ti>; (ii) chloro(alkyls) (irreversible reduction); and (iii) dialkyls (irreversible reduction).

Full text of DOI:10.1039/DT9810000805

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