Zur Reaktivität von Disilylphosphidokomplexen des Eisens und Rutheniums gegenüber 2,4,6-t-Bu3C6H2AsCl2. Bildung und Struktur von Arsaphosphenylkomplexen,Diphosphaarsiranen, Phosphadiarsiranen und 1,2-Diphospha-3,4-diarsetanen

On the Reactivity of Disilylphosphido Complexes of Iron and Ruthenium towards 2,4,6-t-Bu₃C₆H₂AsCl₂. Generation and Structures of Arsaphosphenyl Complexes, Diphospha-ariranes, Phosphadiarsiranes, and 1,2-Diphospha-3,4-diarsetanes The reaction of (η⁵-C₅Me₅)(CO)₂Fe? P(SiMe₃)₂ ( 1a ) with 2,4,6-t-Bu₃C₆H₂AsCl₂ (= Aryl AsCl₂) ( 6 ) leads to the formation of the heterocycles (η⁵-C₅Me₅)(CO)₂Fe? P]₂As-Aryl ( 7a ), (η⁵-C₅Me₅)(CO)₂Fe? P(As-Aryl)₂ ( 8a ), and (η⁵-C₅Me₅)(CO)₂Fe? P-As-Aryl]₂( 9a ). The instable arsaphosphenyl complex (η⁵-C₅Me₅)(CO)₂Fe? P?As-Aryl] can be intercepted as its Cr(CO)₅-adduct 13a . Analogously the ring compounds (η⁵-C₅Me₅)(CO)₂Ru? P]₂(As-Aryl)( 7b ) and (η⁵-C₅Me₅)(CO)₂Ru? P(As-Aryl)₂ ( 8b ) are obtained by treatment of (η⁵-C₅Me₅)(CO)₂Ru? P(SiMe₃)₂ ( 1b ) with 6 . Here again the primarily generated arsaphosphene has to be stabilized by coordination to Cr(CO)₅ which gave E-(η⁵-C₅Me₅)(CO)₂Ru? PCr(CO)₅ = As-Aryl ( E-13b ) and its Z-isomer ( Z-13b ). A comparable reaction sequence furnished the phosphaarsenyl complex (η⁵-C₅Me₅)(CO)(PPh)₃Fe? PCr(CO)₅] = As-Aryl ( 13c ). The molecular structures of 7a and 9a were elucidated by x-ray diffraction analysis. The most interesting feature of 7a is the AsP₂-triangle, in which the As? P(2) bond length (235,0(2) pm) is slightly elongated with respect to the As? P(1) distance (231,6(1) pm). This effect is presumably due to severe steric interactions at the cis-substituted As? P(2) bond. Molecule 9a displays the picture of a bended 1,2-diphospha-3,4-diarsetane (interplanar angle 137.6°) with its substituents in the all trans-orientation. The As? P and P? P separations are normal whereas the As? As bond (249,7(4) pm) is slightly widened with respect to the calculated value for a single bond (ca 244 pm).