# Four-Coordinate Mo(II) as (silox)_{2}Mo(PMe_{3})_{2} and Its W(IV) Congener (silox)_{2}HW(η^{2}-CH_{2}PMe_{2})(PMe_{3}) (silox = ^{t}Bu_{3}SiO)

dataset

posted on 17.11.2008, 00:00 by David S. Kuiper, Peter T. Wolczanski, Emil B. Lobkovsky, Thomas R. CundariThe reduction of [(

*Bu*^{t}_{3}SiO)_{2}MoCl]_{2}(**2**_{2}) provided the cyclometalated derivative, (silox)_{2}HMoMo(κ-O,C-OSi*Bu*^{t}_{2}CMe_{2}CH_{2})(silox) (**3**), and alkylation of**2**_{2}with MeMgBr afforded [(*Bu*^{t}_{3}SiO)_{2}MoCH_{3}]_{2}(**4**_{2}). The hydrogenation of**4**_{2}was ineffective, but the reduction of**2**_{2}under H_{2}generated [(*Bu*^{t}_{3}SiO)_{2}MoH]_{2}(**5**_{2}), and the addition of 2-butyne to**3**gave [(silox)_{2}Mo]_{2}(μ:η^{2}η^{2}-C_{2}Me_{2}) (**6**), thereby implicating the existence of [(silox)_{2}Mo]_{2}(**1**_{2}). The addition of (silox)H to Mo(NMe_{2})_{4}led to (silox)_{2}Mo(NMe_{2})_{2}(**7**), but further elaboration of the core proved ineffective. The silanolysis of MoCl_{5}afforded (silox)_{2}MoCl_{4}(**8**) and (silox)_{3}MoCl_{3}(**9**) as a mixture from which pure**8**could be isolated, and the addition of THF or PMe_{3}resulted in derivatives of**9**as (silox)_{2}Cl_{3}MoL (L = THF,**10**; PMe_{3},**11**). Reductions of**11**and (silox)_{2}WCl_{4}(**15**) in the presence of excess PMe_{3}provided (silox)_{2}Cl_{2}MPMe_{3}(M = Mo,**12**; W,**16**) or (silox)_{2}HW(η^{2}-CH_{2}PMe_{2})PMe_{3}(**14**). While “(silox)_{2}W(PMe_{3})_{2}” was unstable with respect to W(IV) as**14**, a reduction of**12**led to the stable Mo(II) diphosphine, (silox)_{2}Mo(PMe_{3})_{2}(**17**). X-ray crystal structures of**10**(pseudo-*O*_{h}),**12**(square pyramidal), and**14**and**17**(distorted*T*_{d}) are reported. Calculations address the diamagnetism of**12**and**16**, and the distortion of**17**and its stability to cyclometalation in contrast to**14**.