Arsenic complexes oxygen ligands

Inorganic arsenic complexes based on oxygen ligands is scarce. Simple esters of arsenic acid, As(0)(0R)3 (R = Me, Ft, n-Pr, n-Bu, CeHn) have tetragonal structures. Reaction of the diol ligand 2,4-dimethyl-2,4-pentanediol with AsCfr affords an arsenic chloride complex in which the As atom is part of a six-membered ring (37). ... 

The field of cyclopentadienylmetal complexes bearing pendant arsenic or sulfur ligands has remained rather limited up to date. Flowever, their difference from the corresponding phosphane and oxygen representatives could, possibly in combination with other pendant ligands, become a basis for interesting developments in the future. 

Oxygen ligands form very stable complexes with hard Lewis-acid met-alloporphyrins such as Sn(IV), Zr(IV), Mn(III), Mo(V), but also with P(V)-porphyrins. Mixed-metal dimers were synthesized from Al(Me)OEP and phosphorus, arsenic or antimony porphyrins in the form of fi-oxo dimers [73]. hi most cases, polymeric structures are obtained because Sn(IV)-, Mn(III)- and Fe(III)-porphyrins can bind two axial ligands on either side of the porphyrin referred to as trans-binding. This is schematically represented in Fig. 25a. An example includes the linear trinuclear or polymers /r-frans-dioxo-MoTPP [74,75]. 

The relative affinities of various hydroxylic dithiols for arsenite were measured by Zahler and Cleland (33), but proved hard to understand (since seven-membered rings seemed to give the most stable complexes) until Cruse and James (34) showed that an oxygen atom of such a compound acted as a third ligand for arsenic, so that bicyclic complexes were formed. 

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