Lewis acids and bases ionic bonding. Classically, the term "Lewis acid" is restricted to trigonal planar species with an empty p orbital, such as BR where R can be an organic substituent or a halide. For the purposes of discussion, even complex compounds such as EtAlCl and AlCl are treated as trigonal planar Lewis acids. Metal ions such as Na, Mg, and Ce, which are invariably complexed with additional ligands, are often sources of coordinatively unsaturated derivatives that form Lewis adducts upon reaction with a Lewis base[citation needed]. Other reactions might simply be referred to as "acid-catalyzed" reactions. Some compounds, such as HO, are
2011 Super League season results at Millennium Stadium, as part of Magic Weekend<br> B. All St Helens home games in 2011 to be played at Halton Stadium<br> C. Game to be rescheduled for later date, due to Wigan's involvement in the 2011 World Club Challenge 2011 Super League season results This is a list of the 2011 Super League season results. Super League is the top-flight rugby league competition in the United Kingdom and France. The 2011 season started on 12 February, with the Magic Weekend at the Millennium Stadium in Cardiff, and ended on 8 October with the 2011 Super League Grand Final. The