Phosphinines homogeneous catalysis

Abstract Recent developments in the chemistry of phosphinines are reported. This chapter presents and discusses the most important breakthroughs achieved during the last decade. New synthetic approaches allowing the synthesis of polyfunctional phosphinines as well as improvements of well known methods are reported. The use of phosphinines in coordination chemistry is also presented with particular emphasis on their use in the stabilization of low valent and highly reduced transition metal complexes. Another aim of this review is to discuss recent applications of phosphinines, and structures derived directly from phosphinines such as phosphacyclohexadienyl anions and phosphabarrelenes, as ligands in homogeneous catalysis. 

The use of phosphacyclohexadienyl anions as ligands in homogeneous catalysis was also explored. As previously seen, either n- or c-complexes can be formed upon reaction with transition metal precursors depending on the substitution scheme of the phosphinine nucleus. Only one report deals with the catalytic activity of -complexes. In 2005, it was shown that the rf-Rh(I) complex 120 displays a very good catalytic activity in the hydroformylation of terminal and internal olefins. Very high conversion yields and TON were obtained in the hydroformylation of... 

Finally, a last possible use of phosphinines as precursors of phosphines for homogeneous catalysis deals with their transformation into phosphinane. The BASF group showed that alkylation of the phosphorus atom followed by a complete hydrogenation of the ring afforded phosphinanes that showed remarkable activity in the Rh-catalyzed hydroformylation of olefins [109, 110],... 

Interest in the chemistry of the 6ji-phosphinine (phosphabenzene) system has continued, although considerably fewer papers have appeared compared to recent years. The synthesis, coordination chemistry and catalytic applications of phosphi-nines have been reviewed." New chiral bidentate phosphinine ligands (220) have been prepared and their coordination chemistry and applications in rhodium-catalysed asymmetric hydrogenations assessed." The diphosphinine (221) continues to find new applications as a ligand in homogeneous catalysis" and a new mode of coordination to a metal has been identified for the phosphinine (222), two such ligands simultaneously bridging a Mn-Mn bond." ... 

Phosphinine-Based Ligands in Homogeneous Catalysis State of the Art and Future Perspectives... 

The first application of a phosphinine-based catalyst in homogeneous catalysis was reported in 1996 by Zenneck et al. The f/ -phosphinine-iron complex 33 was used in the catalytic [2 -h 2 -h 2] cyclotrimerization of the electron-poor alkyne dimethyl acetylenedicarboxylate to give C6(C02Me)6 and in the co-cyclotrimer-ization of methyl propargylether with butyronitrile affording functionalized pyridine derivatives (Scheme 6.8) [60]. Turnover-numbers of up to 160 for the pyridine derivatives and chemoselectivities of up to 1.4 1 (pyridinesiarenes) were observed. Nevertheless, the efficiency of 33 is significantly lower compared to classical CpCo catalysts [61, 62]. 

A very recent example on the application of phosphinines in homogeneous catalysis was reported by Neumann [69]. The chiral oxazoline-functionalized phosphinine 8 (Fig. 6.5), first reported by Breit et al., was applied in the Ir-catalyzed hydrogenation of several highly substituted unfunctionalized and functionalized alkenes and imines (Scheme 6.17). 

Muller C, Vogt D (2007) Phosphinines as ligands in homogeneous catalysis recent developments, concepts and perspectives. Dalton Trans 5505-5523... 

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