Metallathiirenes. 3.1 Thiocarbamoyl and Alkoxythiocarbonyl Complexes of Molybdenum(II) and Tungsten(II)

Synthetic routes to thiocarbamoyl (thiocarboxamide) complexes of divalent molybdenum and tungsten are reported: The reaction of fac- [Mo(CO) 3 (NCMe) 3 ] with N,N -dimethyl thiocarbamoyl chloride (Me 2 NC( S)Cl) at low temperature provides a thermally labile intermediate ( 1 ) presumed on the basis of subsequent transformations to be [Mo(η 2 -SCNMe 2 )Cl(CO) 3 (NCMe)]. Reactions of 1 with K[HB(pz) 3 ] (pz = pyrazol-1-yl), NaC 5 H 5, bipy, or tmeda provide the complexes [Mo(η 2 -SCNMe 2 )(CO) 2 {HB(pz) 3 }] ( 2 ), [Mo(η 2 -SCNMe 2 )(CO) 2 (η-C 5 H 5 )] ( 3 ), [Mo(η 2 -SCNMe 2 )Cl(CO) 2 (bipy)] ( 4 ), and [Mo(η 2 -SCNMe 2 )Cl(CO) 2 (tmeda)] ( 5 ), respectively. The complex cis,cis,trans- [Mo(η 2 -SCNMe 2 )Cl(CO) 2 (PPh 3 ) 2 ] ( 6 ) results from the oxidative addition of Me 2 NC( S)Cl to [Mo(NCMe) 2 (CO) 2 (PPh 3 ) 2 ] and is one of two isomers obtained from the reaction of 1 with PPh 3 . The complex 2 may also be obtained from reaction of (i) K[Mo(CO) 3 {HB(pz) 3 }] with Me 2 NC( S)Cl; (ii) [Mo(CO) 3 (η 6 -C 7 H 8 )] with Me 2 NC( S)Cl and K[HB(pz) 3 ]; and (iii) K[HB(pz) 3 ] with either 5 or 6 . Sequential treatment of either [Mo(CO) 3 (NCMe) 3 ] or [Mo(CO) 3 (η 6 -C 7 H 8 )] with ClC( S)OR (R = C 6 H 4 Me-4, C 6 H 5 ) and K[HB(pz) 3 ] provides the complexes [Mo(η 2 -SCOR)(CO) 2 {HB(pz) 3 }] [R = C 6 H 4 Me-4 ( 7a ), C 6 H 5 ( 7b )]. Attempts to prepare a mononuclear thiocarbamoyl complex by addition of elemental sulfur or propene episulfide to the aminomethylidyne complex [Mo(⋮CN i Pr 2 )(CO) 2 {HB(pz) 3 }] ( 8 ) were unsuccessful; however addition of [Fe 2 (CO) 9 ] to 8 provided the thermally unstable complex [MoFe(μ-CN i Pr 2 )(CO) 5 {HB(pz) 3 }] ( 9 ), which reacts with sulfur to provide the heterobimetallic bridging thiocarbamoyl complex [MoFe(μ-SCN i Pr 2 )(CO) 5 {HB(pz) 3 }] ( 10 ). Treating fac- [W(CO) 3 (NCMe) 3 ] sequentially with Me 2 NC( S)Cl and K[HB(pz) 3 ] provided [W(η 2 -SCNMe 2 )(CO) 2 {HB(pz) 3 }] ( 11 ); however replacing Me 2 NC( S)Cl with ClC( S)OC 6 H 4 Me-4 led to [WCl(CO) 3 {HB(pz) 3 }] ( 12 ).