Cotton F Albert, Murillo Carlos A, Wang Xiaoping, Wilkinson Chad C
Department of Chemistry and Laboratory of Molecular Structure and Bonding, P.O. Box 30012, Texas A & M University, College Station, TX 77842-3012, USA.
Dalton Trans. 2006 Oct 14(38):4623-31. doi: 10.1039/b608422b. Epub 2006 Aug 9.
The syntheses of two analogues of the bicyclic guanidinate ligand hpp (hpp = the anion of the guanidine-type compound 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2a]pyrimidine) which contain two fused rings are reported. Each compound contains one seven-membered ring while the other is either a five (Htbd) or a six (Htbu) membered ring. In THF/Bu4NPF6, the dimolybdenum compounds Mo2(tbd)4 and Mo2(tbu)4 are easily oxidized and they have signals in the differential pulse voltammograms at -1.059 and -1.009 V (vs. Ag/AgCl), respectively and for the Mo2(5+/6+) couples and in the same order -0.242 and -0.312 V for the Mo2(6+/5+) couples. The two compounds produce the corresponding Mo2(bicyclic guanidinate)4Cl compounds immediately upon dissolution in CH2Cl2 and these easily form species with Mo2(6+) cores. In Mo2(tbd)4Cl there are two crystallographically independent molecules with Mo-Mo distances of 2.1711(7) and 2.1690(7) A. The distance between metal atoms increases to 2.206(1) A upon oxidation to Mo2(tbd)4Cl2 which has a triply bonded Mo2(6+) core. For the diamagnetic compound Mo2(tbu)4 this distance is 2.0677(9) A and it increases to 2.133(2) A upon reduction of the bond order from 4 to 3.5 in the paramagnetic compound Mo2(tbu)4Cl.
报道了两种含有两个稠环的双环胍基配体hpp（hpp = 胍类化合物1,3,4,6,7,8 - 六氢 - 2H - 嘧啶并[1,2a]嘧啶的阴离子）类似物的合成。每个化合物包含一个七元环，而另一个是五元（Htbd）或六元（Htbu）环。在四氢呋喃/四丁基六氟磷酸铵中，二钼化合物Mo2(tbd)4和Mo2(tbu)4很容易被氧化，它们在差分脉冲伏安图中的信号分别出现在 -1.059和 -1.009 V（相对于Ag/AgCl），对应于Mo2(5 + /6 +)电对，而对于Mo2(6 + /5 +)电对，顺序相同，分别为 -0.242和 -0.312 V。这两种化合物在溶解于二氯甲烷后立即生成相应的Mo2(双环胍基)4Cl化合物，并很容易形成具有Mo2(6 +)核心的物种。在Mo2(tbd)4Cl中，有两个晶体学独立的分子，Mo - Mo距离分别为2.1711(7)和2.1690(7) Å。氧化为具有三重键合Mo2(6 +)核心的Mo2(tbd)4Cl2时，金属原子之间的距离增加到2.206(1) Å。对于抗磁性化合物Mo2(tbu)4，该距离为2.0677(9) Å，在顺磁性化合物Mo2(tbu)4Cl中，键级从4降低到3.5时，该距离增加到2.133(2) Å。
