prov:value
| - rom 4 to about 20 carbon atoms, R3 is a bridging group, n is 0, or 1, M is a transition metal having a valence of from 3, 4, 5, or 6, preferably from Group 4, 5, or 6 of the Periodic Table of the Elements and is preferably in its highest oxidation state, Y is a heteroatom containing group in which the heteroatom is an element with a coordination number of three from Group 15 or a coordination numb
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