ADDITION-REACTIONS OF CPMO(NO)(=CXCME(3)) (X=H, D) COMPLEXES WITH HETEROATOM-HYDROGEN BONDS

A mechanistic study of the thermal decomposition of CpMo(NO)(CD(2)CMe(3))(2) in solution provides clear evidence for the formation of CpMo(NO)(=CDCMe(3)). This transient 16-electron neopentylidene complex, either alpha-protio or alpha-deuterio, reads with the heteroatom-hydrogen bonds of amines and alcohols (EHR; R = alkyl, aryl; E = NH, O) to form neopentyl amide and alkoxide complexes of the general form CpMo(NO)(CH(2)CMe(3))(ER). The solid-state molecular structure of CpMo(NO)(CH(2)CMe(3))(NH-p-tolyl) (4) has been determined as a representative three-legged piano-stool molecule in this class. Crystals of 4 are monoclinic, space group P2(1)/c, with a = 11.243(2) Angstrom, b = 9.632(2) Angstrom, c = 16.845(3) Angstrom, beta = 99.74(1)degrees, and Z = 4; R(F) = 0.031 for 2213 data with I-0 greater than or equal to 2.5 sigma(I-0). The pyridine-trapped complexes CpMo-(NO)(=CXCMe(3))(py) (X = H, 2; X = D, 2-d) function as stable synthetic precursors to CpMo-(NO)(=CXCMe(3)) and can thus be derivatized to CpMo(NO)(CXHCMe(3))(ER) complexes (ER = NHR, OR, SCMe(3), OC(O)Me) when reacted with amines, alcohols, thiols, or carboxylic acids, respectively. Reactions with bifunctional reagents produce bimetallic complexes. Thus, treatment of CpMo(NO)(=CHCMe(3)) with neopentyl glycol, hydroquinone, and water provides [CpMo(NO)(CH(2)CMe(3))](2)(mu-X) complexes (X = OCH(2)CMe(2)CH(2)O, OC6H4O, respectively). Labeling studies demonstrate that these conversions involve the addition of the heteroatom-hydrogen bonds to the Mo=C linkage of CpMo(NO)(=CHCMe(3)) in a stereoselective manner rather than protonolysis of the initial dialkyl reagent. The most plausible mechanism for these addition reactions involves initial formation of the EHR adducts CpMo(NO)(=CHCMe(3))-(EHR), followed by subsequent syn E-H addition across the Mo=C linkage.