H©Be 4 S 4 -: A Superhalogen Planar Tetracoordinate Hydrogen Cluster

Abstract

Planar tetracoordinate hydrogen atom (ptH) is rare, with only few example theoretically proposed till date. Herein, we report a planar tetracoordinate hydrogen atom (ptH) as the global minimum H@Be4S4 -cluster. The planar tetracoordinate geometry of the cluster is the global minimum and possess dynamic stability. The ptH geometry is stabilized by 5c-2e multicentre bonding and the cluster can be considered as "superhalogen" with high vertical detachment energy.Planar hypercoordinate atoms (phA) have captivated chemists for decades. [1][2][3][4][5][6] In this regard, planar tetracoordinate carbon (ptC) is the starting example which challenged the known paradigm of chemical structure. It triggers the prediction of many ptCs [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] as the global energy minimum (GEM) and some of them were experimentally synthesized or detected. [10][11][12][13][14][15][16][17] Research has been also directed to other main group elements. Except Ne, all main group elements in the second period have shown this remarkable structural feature. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Recently, Cui and coworkers have predicted the record number (15) of coordination in planar hypercoordinate alkaline earth metals. 40 Recent attention has been directed to the smallest element, hydrogen, in the periodic table. In 2005, Tantillo et al.investigated some nonclassical quasi-planar tetracoordinate hydrogen (ptH) containing carbocations based on cyclooctadiene and tetraene systems. 41 However, the ptH structure is not the lowest energy structure. The first true global minimum ptH geometry has been predicted by us in In4H + . 42 This initiated the research in ptH