Lead(II) nitrate and hexafluorosilicate complexes with neutral diphosphine coordination

摘要

Rare examples of phosphine complexes of lead(II) are reported. The reaction of Pb(NO3)(2) with Me2P-(CH2)(2)PMe2, o-C6H4(PMe2)(2) or Et2P(CH2)(2)PEt2 (L-L) in H2O/MeCN gave white [Pb(L-L)(NO3)(2)], irrespective of the ratio of reagents used. The X-ray structures of [Pb{Me2P(CH2)(2)PMe2}(NO3)(2)] and [Pb-{o-C6H4(PMe2)(2)}(NO3)(2)] reveal chelating diphosphines and kappa(2)-NO3- groups occupying one hemisphere about the lead centre with single oxygen bridges to two further nitrate groups from neighbouring molecules completing a distorted eight-coordinate geometry. Using Pb(SiF6)center dot 2H(2)O produced [Pb-{o-C6H4(PMe2)(2)}(H2O)(SiF6)]center dot H2O which has a chelating diphosphine, the water molecule and a coordinated SiF62- group (which could be described as either kappa(1)- or asymmetric kappa(3)-coordinated to the lead), with further Pb-F interactions to neighbouring molecules producing a chain polymer structure. The structure of [Pb{o-C6H4(PMe2)(2)}(DMF)(2)(SiF6)]center dot DMF was also determined and contains dimers with fluorosilicate bridges. Adventitious oxygen readily form diphosphine dioxide complexes, and the structures of [Pb{Et-2(O)P(CH2)(2)P(O)Et-2}(2)(NO3)(2)] and [Pb{Me2P(CH2)(2)PMe2}{Me-2(O)P(CH2)(2)P(O)Me-2}][BF4](2)center dot 1/2MeNO(2) produced in this way were determined. The former contains eight-coordinate lead with kappa(2)-NO3 groups and bridging diphosphine dioxides, which results in an infinite polymer. In the latter the diphosphine is chelated but the diphosphine dioxide bridges between Pb(II) centres, with coordinated BF4- groups completing a very distorted ten-coordinate moiety. Attempts to isolate similar complexes with o-C6H4(PPh2)(2) or o-C6H4(AsMe2)(2) were unsuccessful.