Synthesis of Homoleptic Neopentoxide and Hydrido-Neopentoxide Trirhenium(III) Clusters.

The purpose of this study was to synthesize Re(3)(&mgr;-OCH(2)CMe(3))(3)(OCH(2)CMe(3))(6) and to determine if it could serve as a source of Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(5) by analogy to Re(3)(&mgr;-O-i-Pr)(3)(O-i-Pr)(6), a previously reported cluster that exists in solution as an equilibrium mixture with Re(3)(&mgr;-O-i-Pr)(3)(H)(O-i-Pr)(5) and acetone. The halide Re(3)(&mgr;-Cl)(3)Cl(6)(THF)(3) reacts at room temperature in THF with 9 equiv of NaOCH(2)CMe(3) to give Re(3)(&mgr;-OCH(2)CMe(3))(3)(OCH(2)CMe(3))(6). An X-ray crystallographic study shows that the core of the homoleptic cluster has virtual D(3h) symmetry, which is consistent with solution NMR data. In refluxing THF, Re(3)(&mgr;-Cl)(3)Cl(6)(THF)(3) reacts with 10 equiv of NaOCH(2)CMe(3) to give [Na(THF)(2)][Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(6)]. The same anionic hydride cluster is also produced when Re(3)(&mgr;-OCH(2)CMe(3))(3)(OCH(2)CMe(3))(6) reacts with excess NaOCH(2)CMe(3) in hot THF. Spectroscopic and X-ray crystallographic data show that [Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(6)](-) has virtual C(s)() core symmetry with a terminal hydride and two terminal alkoxides located at the unique rhenium atom. The hydride and one of the alkoxides have a trans-H-Re-OR arrangement, and in the solid state structure the terminal alkoxide ligands at the unique rhenium atom interact with [Na(THF)(2)](+). It is proposed [Na(THF)(2)][Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(6)] forms when Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(5) or its pivaldehyde adduct, which is generated by neopentoxide beta-hydrogen elimination from Re(3)(&mgr;-OCH(2)CMe(3))(3)(OCH(2)CMe(3))(6), is trapped by NaOCH(2)CMe(3). Crystal data are as follows. C(45)H(99)O(9)Re(3) at -50 degrees C: Pbca (orthorhombic); a = 19.570(2), b = 28.192(3), c = 21.203(3) Å; Z = 8. Na(+)[C(45)H(100)O(9)Re(3)](-).2C(4)H(8)O at -50 degrees C: P&onemacr; (triclinic); a = 13.040(2), b = 14.716(2), c = 19.653(4) Å; alpha = 92.38(1), beta = 92.30(1), gamma = 113.42(1) degrees; Z = 2.