Bis(t-butyl)phosphido complexes of tin(II) and lead(II); analogues of lithium-complexed carbanions

Abstract

The reaction of Li[PBut2] with SnCI2 or PbCI2 in tetrahydrofuran (thf) solution affords the isostructural 'ate' complexes, [Li(thf){E(PB~t,)~}] (E = Sn or Pb), both of which have been characterised by X-ray crystallography.Compared with the transition metals, there are relatively few phosphido derivatives of the heavier main-group elements. We have therefore initiated a survey of the reactions of the [PBut2]-anion with, e.g., the halides of these elements. duMont and co-workers1 have previously reported that the reaction of K[PBuf2] with SnC12 (or Et3PSnC12) in toluene in 2 : 1 stoicheiometry results in the dimer, [ S ~( P B U ~~) ~] ~, for which they proposed structure (1). It was also noted that, under comparable conditions, the reaction of tin dihalides with Li[PBut2] affords But2PSnX. We have now found that in tetrahydrofuran (thf) solution, Li[PBut2] reacts with SnC12 or PbC12 in 3 : 1 stoicheiometry to afford the novel 'ate' complexes, (2) and (3), respectively. X-Ray-quality air-sensitive crystals of orange-yellow (2) and red (3) were grown from n-hexane solutions at -20 "C.?

Low‐Valent Group 14 NHC‐Stabilized Phosphinidenide ate Complexes and NHC‐Stabilized K/P‐Clusters

“…The Sn−P bond in 3 [264.79(28)–266.24(30) pm] is longer than the respective bonds in SIMesPSn( t Bu) 2 Cl or IMesPSnPh 3 [248.2(1) and 245.18(7) pm, respectively], but is in good accordance with the P−Sn distances found in the known ionic compound [Li(thf){Sn(P t Bu 2 ) 3 }] [267.1(1)–270.2(3) pm], or in the heterocubane structures [Sn 4 (PR) 4 ] [P−Sn: 264.6(4)–267.3(5) pm; R=Si(SiMe 3 ) 3 or Si t Bu 2 Ph]. In all these compounds, the tin atoms are threefold‐coordinated exclusively by phosphorus . The Pb−P bond length [274.5(19)–278.3(18) pm] of 4 is in good accordance with corresponding lengths in other compounds described in the literature containing threefold exclusively phosphorus‐coordinated lead atoms, such as [PbPR] 4 [for R=Si t Bu 2 Ph: 271.1(4)–274.6(4) pm; for R=Si(SiMe 3 ) 3 : 271.5(1)–274.1(1) pm], [(thf)Li{Pb(P t Bu) 3 ] [275.8(9)–281.4(6) pm], and [Pb(μ‐P t Bu 2 )P t Bu] 2 [278.1(4)–281.2(3) pm] .…”

“…ÀSn:2 64.6(4)-267.3(5) pm;R = Si(SiMe 3 ) 3 or Si-tBu 2 Ph].I na ll these compounds,t he tina toms are threefoldcoordinated exclusivelyb yp hosphorus [25,26]. The PbÀPb ond length [274.5(19)-278.3(18) pm] of 4 is in good accordance with corresponding lengths in other compounds described in the literature containing threefold exclusively phosphorus-coordinated lead atoms, such as [PbPR] 4 [for R = SitBu…”

A Stabilized Bisphosphanylsilylene and Its Heavier Congeners

“…Single crystals suitable for X-ray diffraction have been obtained for 8 (Figure 3). In the molecular structure of 8 the Si-P distances of 2.3369(8)a nd 2.3275 (8) are elongated comparedw ith the tetravalent dihalosilanes Fe(C 5 H 4 PtBu) 2 SiX 2 (X = Cl, Br,I ;2 .2380(5)-2.2548 (8) ) [5i] and the recently published tetraphosphanyldisilene (2.2666(8)-2.2392(8) ) [16] but are very similart ot hose in NHCa dducts of monophosphanyl substituted silylenes ((2.3460(11) , [14] 2.3748 (7) ) [15] ). One mightb et empted to attribute this elongation to hyperconjugative electron donation from the s PSiP orbital to the electron acceptor N-heterocycle, but second order perturbation theory analysisont he NBO basis reveals only weak( 2-3 kcal mol À1 )i nteractions between the PÀSi bonds and the antibonding orbitals of the NHC unit.…”

“…[5e, g, 7] In trans-2 (2a)t he center of inversioni sl ocated in the middle of the planarf our membered ring with m bridging phosphorus atoms having SnÀPb ond lengths of 2.623(2) and 2.657(2) .F or cis-2 (2b)P endo -Sn distances within the puckered ring are 2.634(5)-2.665 (5) ,w hile the P exo -Sn distances (2.588(6) and 2.600 (5) )a re somewhat shorter, similart o the corresponding distances in the trans isomer (2.601(2) ). All Sn-P contacts in 2 are shorter than those in ar elated atecomplex( 2.671(4)-2.702(3) ) [8] buts ignificantly longer compared to monomericb isphosphanylstannylenes, with (2.4458 (8) ), [4b] or without (2.567 , [2] 2.5757 (7) [4b] )P -Sn p interactions. Within the central P 2 Sn 2 ring, P-Sn-P angles are well below 908 (cis: 7 8.25(16)8,7 8.89(16)8; trans:7 8.65 (8)8)w hile the P exo -Sn-P endo angles are larger (cis:9 6.21(16)8 and 97.32(17)8; trans:1 00.67(7)8)s imilart oo ther cyclic or acyclic P-E-P compounds (E = Si:9 8.54(3) 8-102.46(2)8; [5i] E = Sn: 98.78(4)8; [2a] E = Pb:9 7.84(4)8 [2] ).…”

Heterometallic Tin Compounds: Classification and Analysis of Crystallographic and Structural Data: Part 1. Dimeric Derivatives

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This review covers the crystallographic data for dimeric tin compounds with one other metal atom centre, following the pattern of the previous reviews on tin coordination and organometallic compounds. The first eight derivatives contain tin with lithium [6][7][8][9][10][11][12][13], with the tin in the +2 oxidation state and lithium in its usual +1 oxidation state. The predominant geometries of the tin and the heteroatom are discussed along with the relationships between atom size, bond distances and bond angles.

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