New Strategy to Mixed-Group 6 Metal Carbonyl Telluride Complexes:  Completion of the Trigonal Bipyramidal Clusters [Te₂CrM₂(CO)₁₀]^2- (M = Cr, Mo, W)

Abstract

The new series of tellurium-containing trigonal bipyramidal clusters [Te2CrM2(CO)10]2- (M = Cr, 2a; Mo, 2b; W, 2c) has been synthesized from the ring closure reactions of the ring complexes [Te2Cr2M2(CO)18]2- (M = Cr, 1a; Mo, 1b; W, 1c) in refluxing acetone solutions. The mixed-metal ring complexes [Te2Cr2M2(CO)18]2- (M = Mo, 1b; M = W, 1c) can be obtained readily from the metal expansion reactions of the dichromium complex [Te{Cr(CO)5}2]2- with M(CO)6 (M = Mo, W) in MeCN. The ring complexes [Te2Cr2M2(CO)18]2- (M = Mo, 1b; W, 1c) each display a Te2M2 ring with each Te atom externally coordinated with one Cr(CO)5 group, while the new group 6-containing trigonal bipyramidal clusters [Te2CrM2(CO)10]2- (M = Cr, 2a; Mo, 2b; W, 2c) each consist of a CrM2 trigonal plane capped above and below by two tellurides. Complexes 1b−2c are fully characterized by IR, 125Te NMR spectroscopy, and single-crystal X-ray analysis. This paper describes a new methodology to the highly strained group 6 metal clusters [Te2CrM2(CO)10]2- (M = Cr, 2a; Mo, 2b; W, 2c) from the ring closure reactions of their corresponding ring complexes [Te2Cr2M2(CO)18]2- (M = Cr, 1a; Mo, 1b; W, 1c), and the interesting transformations and structural features of the new complexes 1b−2c are systematically studied as well.

Selenium-capped trimolybdenum and tritungsten carbonyl clusters [Se2M3(CO)10]2− (M=Mo, W)

“…We have recently communicated the first example of the selenium-capped trichromium carbonyl cluster [Se 2 Cr 3 (CO) 10 ] 2À from the treatment of SeO 2 and Cr(CO) 6 in NaOH/MeOH solution [5]. The methodology was straightforward, however, similar strategies to the trimolybdenum and the tritungsten clusters were never successful.…”

“…The methodology was straightforward, however, similar strategies to the trimolybdenum and the tritungsten clusters were never successful. The trichromium cluster [Se 2 Cr 3 (CO) 10 ] 2À was shown to react slowly with Mo(CO) 6 in acetone to give the monomolybdenum-substituted Cr-Mo cluster [Se 2 Cr 2 Mo(CO) 10 ] 2À [5]. To rationalize the formation of the Mo-substituted derivatives, we have examined the reactions of [Et 4 N] [5].…”

“…of Mo(CO) 6 only led to a mixture of products, which was difficult to separate. The mixture was then subjected to 77 Se NMR spectroscopy to contain the monosubstituted product [Et 4 N] 2 [Se 2 Cr 2 Mo(CO) 10 ] (d À108.6), an intermediate species (d À201.9), and the trisubstituted compound [Et 4 N] [Et 4 N] 2 [1] was fully characterized by spectroscopic methods and single-crystal X-ray analysis.…”

“…Contrary to the large number of chalcogen-bridged iron carbonyl clusters, chalcogen-stabilized group 6 metal carbonyl clusters were much fewer mainly due to the lack of rational synthetic routes [1][2][3][4][5][6]. Similar to the paucity of trichromium carbonyl clusters, the homonuclear molybdenum or tungsten carbonyl clusters with the Mo 3 or W 3 ring are also limited, especially for those stabilized by heavier main group elements [4a,7,8].…”

“…Similar to the paucity of trichromium carbonyl clusters, the homonuclear molybdenum or tungsten carbonyl clusters with the Mo 3 or W 3 ring are also limited, especially for those stabilized by heavier main group elements [4a,7,8]. Although the Se-capped trichromium carbonyl closo-cluster [Se 2 Cr 3 -(CO) 10 ] 2À was obtained from the direct reaction of SeO 2 with Cr(CO) 6 in basic methanol solution [5], the trimolybdenum and tritungsten congeners have never been achieved by similar methodologies. In this study, we will describe the facile metal-metal exchange reactions for the synthesis of the first selenium-capped trimolybdenum and tritungsten carbonyl clusters, in which an intermediate species is isolated to provide some valuable mechanistic information.…”