Structure and bonding of chemical compounds has always been a central part of study in chemistry. Since the birth of the Lewis structure a century ago, chemists already have a systematic way to describe the features of chemical bondings for numerous chemical compounds. On the other hand, within the past few decades, a large multitude of atypical chemical compounds, many of those being coordination and nanocluster compounds, that do not follow the simple rules proposed by Lewis a century ago are discovered. In this dissertation, several representative classes of coordination and nanocluster compounds are selected for study, with governing rules ranging from simple two-center-two-electron bonds, through electron-deficient cases including the Wade-Mingos rule and the jellium model,...[ Read more ]

Structure and bonding of chemical compounds has always been a central part of study in chemistry. Since the birth of the Lewis structure a century ago, chemists already have a systematic way to describe the features of chemical bondings for numerous chemical compounds. On the other hand, within the past few decades, a large multitude of atypical chemical compounds, many of those being coordination and nanocluster compounds, that do not follow the simple rules proposed by Lewis a century ago are discovered. In this dissertation, several representative classes of coordination and nanocluster compounds are selected for study, with governing rules ranging from simple two-center-two-electron bonds, through electron-deficient cases including the Wade-Mingos rule and the jellium model, to nanoclusters with fragments held together by more subtle orbital interactions. Within each of these classes, we have reviewed the applicability and limitations of each rule, and also considered possible extensions within each case that could find support from quantum chemical calculations as well as reported examples from literature. Over all these studies, we have explored the possibility of formulating localized models for understanding all these reported examples, and compared our localized approaches against the more delocalized molecular orbital descriptions available from quantum chemical calculations. We showed how a localized approach can complement usual quantum chemical calculations and give guidance on further research directions. We anticipate the proposed models and analysis could aid the understanding in structure and bonding of a much wider range of examples of coordination and nanocluster compounds.