Agostic interactions multiple

Compound 61 discussed previously (see Section 2.10) also exhibits multiple agostic interactions. This Nd complex has seven agostic bonds arising from C-H groups of three different ligand systems. 

Multiple agostic interactions are common, in which case each interaction may represent fractional donation of electron pairs and is correspondingly weaker (longer M-H and M-C distances). In some cases hydrogen bonding between M and the proton may predominate, as found by Brammer in [R3N-H+ Co(CO)4], where Co-H is 2.613(2) A by neutron diffraction.21 In this case and others (see Section... 

Recently, several complexes with an agostic Si-H-M have appeared in the literature [85]. The majority of them has at least one SiMe2 bridging ligand. Yttrium complex 26 exhibits unusual multiple Si-H-M agostic interactions, which were characterized by X-ray structural determination and other spectroscopic methods... 

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