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

Rare examples of phosphine complexes of lead(II) are reported. The reaction of Pb(NO3)2 with Me2P(CH2)2PMe2, o-C6H4(PMe2)2 or Et2P(CH2)2PEt2 (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)2PMe2}(NO3)2] and [Pb{o-C6H4(PMe2)2}(NO3)2] reveal chelating diphosphines and κ(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)·2H2O produced [Pb{o-C6H4(PMe2)2}(H2O)(SiF6)]·H2O which has a chelating diphosphine, the water molecule and a coordinated SiF6(2-) group (which could be described as either κ(1)- or asymmetric κ(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)]·DMF was also determined and contains dimers with fluorosilicate bridges. Adventitious oxygen readily form diphosphine dioxide complexes, and the structures of [Pb{Et2(O)P(CH2)2P(O)Et2}2(NO3)2] and [Pb{Me2P(CH2)2PMe2}{Me2(O)P(CH2)2P(O)Me2}][BF4]2·½MeNO2 produced in this way were determined. The former contains eight-coordinate lead with κ(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.