34 No. 2
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IUPAC Chemical Nomenclature and Structure Representation Division (Division VIII) is tasked with the development of unambiguous structure-based chemical nomenclature for a scientific community, which, by habit, establishes its own naming conventions as the need arises. Accordingly, the division’s work has to be conducted against a background of names, the usage of which is entrenched in the literature and which in many instances will be retained regardless of IUPAC recommendations. Nowhere is this more evident than in the naming of polymers, for which structure-based nomenclature has limited applicability such that the polymer community has long-preferred source-based over structure-based nomenclature.
By working in cooperation with the Polymer Division, source-based nomenclature of organic polymers has been systematized such that the two systems now sit comfortably side-by-side. However, the same cannot be said of the nomenclature of inorganic and coordination polymers for which only a structure-based system has been elaborated. To date, the recommended nomenclature of regular single-strand inorganic and quasi-single-strand inorganic and coordination polymers is governed for the most part by the same fundamental principles as those of single-strand organic polymers. The names are those of constitutional repeating units (CRU) prefixed by ‘poly’, but also by catena for linear chains, and where necessary with other structural descriptors and designations for end groups. Quite properly, the CRUs are named by the nomenclature rules for inorganic and coordination chemistry, which differ from those of organic chemistry. However, the catena prefix is redundant and has been rarely if ever used by the polymer community. In the 1985 document there are also names such as oxo, chloro, and bromo which in the 2005 edition of the Red Book have been superseded.
There are new metallocene-based polymers, particularly those of ferrocene, which have by custom been accorded source-based names [e.g., poly(ferrocenyldimethylsilane)], thereby using one of the methods of organic polymer nomenclature. Likewise, there are new inorganic-organic hybrid polymers for which nomenclature rules have never been elaborated. In addition, the inconsistencies that arise from the preferences of the polymer community set against the rigorous requirements of an exclusively structure-based nomenclature system are abundant and evident. By way of illustration, the polymer—[Si(CH3)2O]n —would now be named by inorganic chemists as catena-poly[(dimethylsilicon)-μ-oxido], by polymer chemists familiar with organic structure-based nomenclature as poly[oxy(dimethylsilanediyl)], and in accordance with tradition as poly(dimethylsiloxane). Thus, notwithstanding the need to update the 1985 document (Pure Appl. Chem. 57, 149–168 (1985); doi:10.1351/pac198557010149) and given the very significant advances in the subject area that have been made since that date, this is the right time to start rethinking the recommended nomenclature of tractable inorganic and coordination polymers that addresses the practices of the polymer community while respecting the concerns and requirements of inorganic chemists, whose interests in such macromolecules often stem from a quite different perspective.
last modified 5 March 2012.
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