Lead(ii) nitrate and hexafluorosilicate complexes with neutral diphosphine coordination†
Abstract
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 κ2-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 SiF62− group (which could be described as either κ1- or asymmetric κ3-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 κ2-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.
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