Diphosphine and Diarsine Complexes of Germanium(II) Halides—Preparation, Spectroscopic, and Structural Studies

Abstract

The Ge(II) halide complexes [GeX(2)(L-L)] (L-L = o-C(6)H(4)(PPh(2))(2), o-C(6)H(4)(PMe(2))(2), Me(2)P(CH(2))(2)PMe(2); X = Cl, Br, I. L-L = Et(2)P(CH(2))(2)PEt(2); X = Cl or Br. L-L = o-C(6)H(4)(AsMe(2))(2); X = Br or I) and [GeCl(L-L)][GeCl(3)] (L-L = o-C(6)H(4)(AsMe(2))(2)) have been prepared and characterized by IR, (1)H and (31)P{(1)H} NMR spectroscopy, and microanalyses. The crystal structures of [GeX(2){o-C(6)H(4)(PPh(2))(2)}] (X = Cl, Br, I) reveal discrete mononuclear units with a very asymmetric bidentate o-C(6)H(4)(PPh(2))(2) ligand and a bent GeX(2) unit. Those of [GeX(2){o-C(6)H(4)(PMe(2))(2)}] show symmetrically coordinated diphosphine with loosely associated dimer arrangements, formed through long Ge...X bridges between adjacent monomer units. [GeX(2){R(2)P(CH(2))(2)PR(2)}] (R = Me; X = Cl, Br, I. R = Et; X = Cl, Br) all show discrete monomer structures with 2-fold crystallographic symmetry and based upon four-coordinate Ge, with the diphosphine chelating and approximately linear GeX(2) units. [GeI(2){o-C(6)H(4)(AsMe(2))(2)}] involves significant intermolecular Ge...I interactions, giving rise to a zigzag polymer chain. Finally, the structure of [GeCl{o-C(6)H(4)(AsMe(2))(2)}][GeCl(3)] shows pyramidal cations and anions both with crystallographic mirror symmetry, with the diarsine symmetrically chelating, and long Ge...Cl interactions give a loosely associated chain polymer with alternating cations and anions. Comparisons across this series of structurally diverse complexes are discussed.

Coordination chemistry of the main group elements with phosphine, arsine and stibine ligands

“…The core structure of [GeI 2 {Me 2 P(CH 2 ) 2 PMe 2 }] is similar but the geometry shows very long iodo-bridges forming dimer units. For all of these alkyl substituted diphosphine complexes, the 31 P{ 1 H} NMR spectra show singlets with large high frequency coordination shifts, which was interpreted as evidence for five-membered chelate rings present in solution [277].…”

“…48) [277]. The core structure of [GeI 2 {Me 2 P(CH 2 ) 2 PMe 2 }] is similar but the geometry shows very long iodo-bridges forming dimer units.…”

“…The 31 P NMR spectra of these three complexes show singlets with small high frequency coordination shifts even at low temperatures, which suggests that exchange between the two phosphine groups is fast in solution. In contrast, the very strong -donor o-C 6 H 4 (PMe 2 ) 2 chelates to GeX 2 (X = Cl, Br or I) [277]; the isomorphous chloride and bromide complexes are halide-bridged dimers ( Fig. 46) with the germanium core of P 2 X 2 and a long bond to a third X, whereas the iodo-complex has a similar core, but with very long Ge•••I bridges, just within the van der Waals radii sum (Fig.…”

“…45) [277] in which the Ge − P distances differ by ∼0.6Å, with the second phosphine group interacting weakly [3 + 1 coordination]. The 31 P NMR spectra of these three complexes show singlets with small high frequency coordination shifts even at low temperatures, which suggests that exchange between the two phosphine groups is fast in solution.…”

“…The diarsine o-C 6 H 4 (AsMe 2 ) 2 forms [GeX 2 {o-C 6 H 4 (AsMe 2 ) 2 }] for X = Br or I, which have an As 2 X 2 core similar to that in the alkyldiphosphine complexes, but are further weakly associated via halide bridges into a polymer chain [277]. Surprisingly [278].…”