Nitrogen, phosphorus, arsenic, antimony and bismuth

Abstract

This chapter reviews the literature reported during 2007 on the chemistry of nitrogen, phosphorus, arsenic, antimony and bismuth. HighlightsOnce again there has been considerable development in the chemistry of the Group 15 elements, and a notable highlight has been the continued studies by the group of Cummins into the use of early transition metal amido complexes as transfer agents for nitride, phosphide and related ligands. [1][2][3] NitrogenA review of the recent advances in the activation of N 2 by Group 4 metal complexes has been published. 4 The reaction of [(Z 5 -C 5 Me 4 H) 2 Hf] 2 (m-Z 2 :Z 2 -N 2 ) with CO 2 results in the insertion of two equivalents of CO 2 into Hf-N bonds and formation of 1. 5 Importantly, reaction of 1 with Me 3 SiI results in the ultimate formation of (Z 5 -C 5 Me 4 H) 2 HfI 2 and (Me 3 Si) 2 NN(CO 2 SiMe 3 ) 2 . Reduction of Zr[NPN]*Cl 2 with KC 8 in thf solution under an atmosphere of N 2 leads to the formation {[NPN]*Zr(THF)} 2 (m-Z 2 :Z 2 -N 2 ). 6 The N-N bond length in this species is 1.503(6) A ˚which corresponds to a formal reduction to N 2 4À. The dinitrogen complex [Me 2 Si(Z 5 -C 5 Me 4 )(Z 5 -C 5 H 3 -3-t Bu)Zr] 2 (m-Z 2 :Z 2 -N 2 ) has also been prepared and reacts with H 2 under ambient conditions to give [Me 2 Si(Z 5 -C 5 Me 4 )(Z 5 -C 5 H 3 -3-t Bu)ZrH] 2 (m-Z 2 :Z 2 -N 2 H 2 ). 7 An important feature of this chemistry is the contrast with a related dinitrogen complex which contains less electron donating cyclopentadienyl ligands. In this latter case, as there is less electron density on the N 2 it is more weakly bound to the metal and hydrogenation results in the displacement of N 2 and the formation of the corresponding zirconium dihydride. Reduction of the tantalum complex Cp*TaCl 3 (L) (L = N i PrC{Me}N i Pr) with 2.5 equivalents of KC 8 under N 2 results in the formation of the dimeric complex 2, whereas higher temperature and 4 equivalents of KC 8 result in the formation of 3: other reduction products were also obtained and fully characterised. 8 Reactions of both zirconium and hafnium complexes containing related ligand sets to this tantalum example have also been investigated. 9 A niobium hydride complex, supported by tripodal alkoxide ligands, has also been shown to react with N 2 to give a similar formal N-N cleavage. 10 Further examples of N 2 fixation at chromium, 11 titanium, 12 vanadium, 13 and samarium 14 have all been reported. A theoretical study into the design of complexes which will bind N 2 but also allow for subsequent hydrogenation has been published 15 as has a