Neutral Pentacoordinate Silicon Fluorides Derived from Amidinate, Guanidinate, and Triazapentadienate Ligands and Base-Induced Disproportionation of Si2Cl6 to Stable Silylenes

Rajendra S Ghadwal,Peter G Jones,Birger Dittrich,Kevin Pröpper,Herbert W Roesky

doi:10.1021/ic1020548

Rajendra S Ghadwal, Peter G Jones + Show 3 more

Open Access

https://doi.org/10.1021/ic1020548

Copy DOI

Abstract

Pentacoordinate silicon fluorides L(1)SiF(3) (2a), L(2)SiF(3) (2b), and (L(3)SiF(2))(2) (2c)(2) based on amidinate (L(1) = PhC(N(t)Bu)(2)), guanidinate (L(2) = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate), and triazapentadienate (L(3) = NC(NMe(2))NC(NMe(2))NAr; Ar = 2,6-(i)Pr(2)C(6)H(3)) ligands were prepared by fluorination of the corresponding chlorosilanes L(1)SiCl(3) (1a), L(2)SiCl(3) (1b), and L(3)SiCl(2) (1c) with Me(3)SnF at ambient temperature. Compounds 1b, 1c, 2a, 2b, and (2c)(2) were characterized by (1)H, (13)C, (19)F, and (29)Si NMR spectroscopic studies. Molecular structures of 1b, 1c, 2a, and (2c)(2) were determined by single crystal X-ray structural analysis. Invariom refinement involving non-spherical scattering factors of the Hansen-Coppens multipole model was performed for 1b. Compound L(3)SiF(2) (2c) is dimeric both in the solid state and in solution, whereas its chloro-analogue 1c is monomeric. The attempted synthesis of diamidinatotetrachlorodisilane by reaction of lithium amidinate with Si(2)Cl(6) led to the formation of the silane (1a) and the silylene L(1)SiCl (3). Reaction of Si(2)Cl(6) with N-heterocyclic carbenes (NHC) afforded NHC adducts of dichlorosilylene and SiCl(4). A one pot method for the preparation of base-stabilized silylenes from Si(2)Cl(6) is discussed.

Highlights

Compounds with coordination numbers greater than four at the silicon have received considerable attention during the past few decades
For compound 1b, the Independent Atom Model (IAM) refinement starting values were used for Invariom refinement[15] which is based on the Hansen and Coppens multipole formalism.[16]
In the Invariom refinement multipole parameters are fixed at theoretically predicted values, and only the positional and displacement parameters are refined, providing a more accurate structural model

Summary

Introduction

Compounds with coordination numbers greater than four at the silicon have received considerable attention during the past few decades. By donor atoms (C, N, or P) have proved to be attractive topics of research Further progress in this field is driven by the design and synthesis of new compounds with main group elements. J. P.; Kpoton, A.; Poirier, M.; Royo, G.; Young, J. G. In The Chemistry of Organic Silicon Compounds; Patai, S., Rappoport, Z., Eds.; John Wiley & Sons Ltd.: New York, 1989; Part 1, pp 839-892. C. In The Chemistry of Organic Silicon Compounds; Patai, S., Rappoport, Z., Eds.; John Wiley & Sons: Chichester, U.K., 1989; Part 2, pp 1241-1288. (5) Kocher, N.; Henn, J.; Gostevskii, B.; Kost, D.; Kalikhman, I.; Engels, B.; Stalke, D. In Main Group Metals in Organic Synthesis; Yamamoto, H., Oshima, K., Eds.; Wiley-VCH: Weinheim, 2004; Vol 2, 409-592. As a continuation of these studies, we report a new method for the preparation of base-stabilized silylenes from Si2Cl6

Experimental Section

Results and Discussion

Conclusion