1. For recent reviews and leading references see: (a) P.R. Meehan, D.R. Aris, G.R. Willey, Coord. Chem. Rev. 181 (1999) 121;
2. (b) S.A. Cotton, Polyhedron, 18 (1999) 1691;
3. (c) F.T. Edelmann, in: E.W. Abel, F.G.A. Stone, G. Wilkinson (Eds.), Comprehensive Organometallic Chemistry, 2nd ed., vol. 4, 1995, p. 10;
4. (d) F.A. Hart, in: R.D. Gillard, J.A. McCleverty, G. Wilkinson (Eds.), Comprehensive Coordination Chemistry, vol. 3, Pergamon, Oxford, 1987, p. 1059;
5. (e) F.G.N. Cloke, in: E.W. Abel, F.G.A. Stone, G. Wilkinson (Eds.), Comprehensive Organometallic Chemistry, 2nd ed., vol. 4, 1995, p. 1.