The preparations and spectroscopic characterisation of the hydrolytically unstable As(III) complexes, [AsF3(OPR3)2] (R = Me or Ph) and [AsF3{Me2P(O)CH2P(O)Me2}] are described and represent the first examples of complexes of AsF3 with neutral ligands. The crystal structure of [AsF3{Me2P(O)CH2P(O)Me2}] contains dimers with bridging diphosphine dioxide, but there are also long contacts between the dimers to neighbouring phosphine oxide groups, completing a very distorted six-coordination at arsenic and producing a weakly associated polymer structure. The reaction of AsF3 with OAsPh3 affords Ph3AsF2, and no arsine oxide complex was formed. Reaction of SbF3 with OER3 (R = Me or Ph, E = P or As), Me2P(O)CH2P(O)Me2 and Ph2P(O)(CH2)nP(O)Ph2 (n = 1 or 2) in MeOH produces [SbF3(OER3)2], [SbF3{Me2P(O)CH2P(O)Me2}] and [SbF3{Ph2P(O)(CH2)nP(O)Ph2}] respectively. The X-ray structures reveal that the complexes contain square pyramidal SbF3O2 cores with apical F and cis disposed pnictogen oxides. However, whilst [SbF3(OER3)2] (R = Ph: E = P or As; R = Me: E = As) and [SbF3{Ph2P(O)CH2P(O)Ph2}] are monomeric, [SbF3{Me2P(O)CH2P(O)Me2}] is a dimer with bridging diphosphine dioxides producing a twelve-membered ring, and [SbF3{Ph2P(O)(CH2)2P(O)Ph2}] is a chain polymer with diphosphine dioxide bridges. In the OAsR3 reactions with SbF3, R3AsF2 are also formed. Notably the Sb–O(P) bonds are shorter than As–O(P), despite the covalent radii (As < Sb), consistent with very weak coordination of the AsF3. IR and multinuclear (1H, 19F and 31P) NMR data are reported and discussed. BiF3 does not react with pnictogen oxide ligands under similar conditions and halide exchange of bismuth chloro complexes with Me3SnF gave BiF3.

The preparations and spectroscopic characterisation of the hydrolytically unstable As(III) complexes, [AsF3(OPR3)2] (R = Me or Ph) and [AsF3{Me2P(O)CH2P(O)Me2}] are described and represent the first examples of complexes of AsF3 with neutral ligands. The crystal structure of [AsF3{Me2P(O)CH2P(O)Me2}] contains dimers with bridging diphosphine dioxide, but there are also long contacts between the dimers to neighbouring phosphine oxide groups, completing a very distorted six-coordination at arsenic and producing a weakly associated polymer structure. The reaction of AsF3 with OAsPh3 affords Ph3AsF2, and no arsine oxide complex was formed. Reaction of SbF3 with OER3 (R = Me or Ph, E = P or As), Me2P(O)CH2P(O)Me2 and Ph2P(O)(CH2)nP(O)Ph2 (n = 1 or 2) in MeOH produces [SbF3(OER3)2], [SbF3{Me2P(O)CH2P(O)Me2}] and [SbF3{Ph2P(O)(CH2)nP(O)Ph2}] respectively. The X-ray structures reveal that the complexes contain square pyramidal SbF3O2 cores with apical F and cis disposed pnictogen oxides. However, whilst [SbF3(OER3)2] (R = Ph: E = P or As; R = Me: E = As) and [SbF3{Ph2P(O)CH2P(O)Ph2}] are monomeric, [SbF3{Me2P(O)CH2P(O)Me2}] is a dimer with bridging diphosphine dioxides producing a twelve-membered ring, and [SbF3{Ph2P(O)(CH2)2P(O)Ph2}] is a chain polymer with diphosphine dioxide bridges. In the OAsR3 reactions with SbF3, R3AsF2 are also formed. Notably the Sb–O(P) bonds are shorter than As–O(P), despite the covalent radii (As < Sb), consistent with very weak coordination of the AsF3. IR and multinuclear (1H, 19F and 31P) NMR data are reported and discussed. BiF3 does not react with pnictogen oxide ligands under similar conditions and halide exchange of bismuth chloro complexes with Me3SnF gave BiF3.