Silylated dimers, solid-state structure

Similar reactions between Ni(GDT) and the silyl-substituted di- or trialkynes SiPh2(G=G-R)2 (R = Bu or SiMe3) and SiPh(G=G-Bu )3 have led to the preparation of the homoleptic Ni(0)-alkyne dimers whose solid-state structures are not influenced by the intermolecular O-H interactions, as shown in 33. The analogous reactions between Ph3Si-G=G-Bu and Ni(cod)2 or Ni(GDT) give the monomeric compounds 34 and 35. 

Figure 4.7 Solid-state structure of silylated ureidopyrimidinone dimers (a-d) and comparison of the XRD powder patterns of molecular precursor and organo-sllica resulting from the hydrolysis-condensation. (Reproduced from Ref. [61] with permission of the PCCP Owner Societies.)...

These new silyl complexes are monomeric in benzene solution, but are dimeric in the solid state. The crystal structure of the samarium analogue (Figure 1) shows that dimers form via intermolecular Sm-CH3-Si interactions. The Sm-Si distance, 3.052 (8) A, is to our knowledge the longest metal-silicon distance known. As with other complexes that display Ln-CH3-Si interactions in the solid state, evidence for these interactions in solution is not observed in NMR spectra. The [H NMR chemical shifts for the neodymium... 

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