| http://www.w3.org/ns/prov#value | - st as bulky as a t-butyl radical; R is a structural bridge between the (C5 R4) and (R'2 C5 C4 R'4) rings to impart stereorigidity and, preferably, is a hydrocarbyl or hydrosilyl radical having one carbon or silicon atom to form the bridge; Q is a hydrocarbyl radical, such as an alkyl, aryl, alkenyl, alkylaryl or arylalkyl radical having 1-20 carbon atoms or is a halogen; Me is a Group IIIB, IVB,
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