Majumdar Amit, Pal Kuntal, Nagarajan Kowliki, Sarkar Sabyasachi
Department of Chemistry, IIT Kanpur, Kanpur, India.
Inorg Chem. 2007 Jul 23;46(15):6136-47. doi: 10.1021/ic7006777. Epub 2007 Jun 20.
Two series of thiol-bridged dimeric desoxo molybdenum(IV) and tungsten(IV) bis(dithiolene) complexes, Et(4)N[M(IV)(2)(SR)(2)(mnt)(4)] [M = Mo, R = (1) -Ph, (2) -CH(2)Ph, (3) -CH(2)CH(3), (4) -CH(2)CH(2)OH; M = W, R = (1a) -Ph, (2a) -CH(2)Ph, (3a) -CH(2)CH(3), (4a) -CH(2)CH(2)OH] and one monomeric desoxo complex, Et(4)N[WIV(SPh)(2)(mnt)(2)] (5a) are reported. These complexes are diamagnetic, and crystal structures of each of the complex (except 5a) exhibits a dimeric {M(IV)(2)(SR)(2)} core without any metal-metal bond where each metal atom possesses hexa coordination. The M-SR distance ranges from 2.437 to 2.484 Angstrom in molybdenum complexes and from 2.418 to 2.469 Angstrom in tungsten complexes. These complexes display Mo-S(R)-Mo angles ranging from 92.84 degrees to 96.20 degrees in the case of 1-4 and W-S(R)-W angles ranging from 91.20 degrees to 96.25 degrees in the case of 1a-4a. Interestingly, both the series of Mo(IV) and W(IV) dimeric complexes respond to an unprecedented interconversion between the dimer and the corresponding hexacoordinated monomer upon change of pH. This pH-dependent interconversion establishes the fact that even the pentacoordinated Mo(IV) and W(IV) bis(dithiolene) moieties are forced to dimerize; these can easily be reverted back to the corresponding monomeric complex, reflecting the utility of dithiolene ligand in stabilizing the Mo(IV)/W(IV) moiety in synthesized complexes similar to the active sites present in native proteins.
报道了两系列硫醇桥联的二聚脱氧钼（IV）和钨（IV）双（二硫烯）配合物，Et(4)N[M(IV)(2)(SR)(2)(mnt)(4)] [M = Mo，R = (1) -Ph，(2) -CH(2)Ph，(3) -CH(2)CH(3)，(4) -CH(2)CH(2)OH；M = W，R = (1a) -Ph，(2a) -CH(2)Ph，(3a) -CH(2)CH(3)，(4a) -CH(2)CH(2)OH] 以及一个单体脱氧配合物，Et(4)N[WIV(SPh)(2)(mnt)(2)] (5a)。这些配合物是抗磁性的，并且每个配合物（除5a外）的晶体结构都呈现出一个没有任何金属 - 金属键的二聚{M(IV)(2)(SR)(2)}核心，其中每个金属原子具有六配位。钼配合物中的M - SR距离在2.437至2.484埃之间，钨配合物中的M - SR距离在2.418至2.469埃之间。在1 - 4的情况下，这些配合物的Mo - S(R) - Mo角范围为92.84°至96.20°，在1a - 4a的情况下，W - S(R) - W角范围为91.20°至96.25°。有趣的是，Mo(IV)和W(IV)二聚配合物系列在pH值变化时都出现了前所未有的二聚体与相应六配位单体之间的相互转化。这种pH依赖性的相互转化证实了即使是五配位的Mo(IV)和W(IV)双（二硫烯）部分也被迫二聚；它们可以很容易地再转化回相应的单体配合物，这反映了二硫烯配体在稳定合成配合物中Mo(IV)/W(IV)部分方面的作用，类似于天然蛋白质中存在的活性位点。
