Chemistry Department, Babes-Bolyai University, Romania
*Corresponding author: Ionel Haiduc, Chemistry Department, Babes-Bolyai University, Romania
Submission: October 17, 2021;Published: October 27, 2021
Volume2 Issue5October, 2021
I would like to draw attention to the novel chemical concept of inverse coordination, which discloses another face of coordination chemistry (practically ignored so far as a distinct field) and deals with the formation of metal complexes in which the donor and acceptor positions are reversed. This concept emerged after R.C. Mulvey used the “inverse crown” paradigm , to describe macrocyclic structures in which “the arrangement of Lewis acidic [acceptor] and Lewis basic [donor] sites is opposite to that encountered in conventional crown ether complexes”. The extension of this paradigm resulted in the “inverse coordination” concept . The inverse coordination can be defined as the formation of metal complexes in which the arrangement of the acceptor and donor sites is opposite to that occurring in conventional coordination complexes . The relationship between traditional coordination complexes and inverse coordination complexes could be regarded as a Janus face image, as suggested by Scheme 1.
Scheme 1:A Janus* face relationship between traditional and inverse coordination complexes. *Janus-Roman god of beginnings and transitions, God of change and time (Wikipedia).
The inverse coordination covers a broad diversity of complexes which can be classified according to the central core, which can be a distinct single atom or a di- or polytopic donor molecule. Several classes of inverse coordination complexes have been reviewed in a book  , a general review  and several articles, namely dealing with oxygen [3,6], sulfur, selenium , halogens , nitrogen , phosphorus and other pnictogen (arsenic, antimony)  single atoms, as well as polytopic exo-donor molecules with oxygen heteroatoms, i.e. oxo-carbons and oxygen heterocycles , oxalates and thio and azo analogues , nitrogen donor molecules (e.g. five-membered  and six-membered  nitrogen heterocycles) and inorganic open and cyclic heteroatom molecules  as coordination centers. The inverse coordination complexes should be regarded as a distinct chapter within the broad discipline of coordination chemistry.
© 2021 Ionel Haiduc. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and build upon your work non-commercially.