The high-yield product of the reaction of [RuCl 2 (dmso) 4 ] (dmso ) dimethylsulfoxide) with Na[HB(mt) 3 ] (mt ) methimazolyl) is not, as reported, the complex [RuCl(dmso) 2 {κ 3 -S,S′,S′′-HB(mt) 3 }] but rather the isomeric [RuCl(dmso) 2 {κ 3 -H,S,S′-HB(mt) 3 }], which features a three-center, two-electron B-H-Ru interaction, as also found for the complex [RuH(PPh 3 ) 2 {κ 3 -H,S,S′-H 2 B(mt) 2 }], which results from [RuHCl(PPh 3 ) 3 ] and Na[H 2 B(mt) 2 ].

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A side-product that accompanies the synthesis of the widely utilized starting material TpRu(PPh 3 ) 2 Cl (Tp ) hydridotris(pyrazolyl)borate) has been identified as the complex Cl TpRu(PPh 3 ) 2 H ( Cl Tp ) chlorotris(pyrazolyl)borate), which proVides a rare example of a boron-halogenated pyrazolylborate ligand. The reaction of Cl TpRu(PPh 3 ) 2 H with dichloromethane or chloroform quantitatiVely produce Cl TpRu(PPh 3 ) 2 Cl.

The reaction of [RuCl 2 (PPh 3 ) 3 ] with K[H 2 B(pz) 2 ] (pz=pyrazol-1-yl) in tetrahydrofuran at room temperature provides the known hydrotris(pyrazolyl)borate complex [RuH(PPh 3 ) 2 {HB(pz) 3 }] (1b) via pyrazole scrambling. In contrast, the reaction of [RuCl 2 (PPh 3 ) 3 ] with K[H 2 B(pz) 2 ] in methanol does not, as previously reported, provide [Ru(PPh 3 ) 2 {H 2 B(pz) 2 } 2 ] but, rather, a mixture of the complexes [RuX(PPh 3 ) 2 {κ 3 O,N,N 0 -(MeO) 2 B(pz) 2 }] (X = H (2a), Cl (2b)) and ttt-[RuCl 2 (Hpz) 2 -(PPh 3 ) 2 ] (3), each of which have been structurally characterized. Although the resulting bulk admixtures of 2a,b have so far proved inseparable, treatment with mercuric chloride cleanly converts the 2a component to 2b. Heating 2b with 1,2-bis(dicyclohexylphosphino)ethane (dcpe) results in substitution of both phosphine ligands and the formation of [RuCl(dcpe){κ 3 O,N,N 0 -(MeO) 2 B(pz) 2 }] (4) in which the ruthenium-ether linkage is ultimately retained.

The syntheses of a range of poly(methimazolyl)borate -ligated nitrosyl complexes of tungsten and molybdenum are reported, the characterization of which includes the crystal structure determinations of the compounds [W(NO)(CO) 2 {κ 3 -S,S′,S′′-HB(mt3 }], [W(NO)(CO) 2 (PPh 3 ){κ 2 -S,S′-H 2 B(mt) 2 }], and [Mo(NO-)(CO) 2 {κ 3 -H,S,S′-H 2 B(mt) 2 }] (mt ) methimazoyl). The reaction of [W(NO)(CO) 3 (PPh 3 ) 2 ]PF 6 with Na[HB(mt) 3 ] and Na[H 2 B(mt) 2 ] provides respectively [W(NO)(CO) 2 {HB(mt) 3 }] and [W(NO)(CO) 2 (PPh 3 ){κ 2 -S,S′-H 2 B(mt) 2 }]. The complexes [M(NO)(CO) 2 {HB(mt) 3 }] and [M(NO)(CO) 2 {κ 3 -H,S,S′-H 2 B(mt) 2 }] (M ) W, Mo) arise from the reactions of Na[M(CO) 3 {H 2 B(mt) 2 }] with N-methyl-N-nitrosotoluenesulfonamide. The molybdenum complex [Mo(NO)(CO) 2 {HB(mt) 3 }] is also obtained unexpectedly from the reaction of [Mo(η 3 -C 3 H 5 )(CO) 2 {HB(mt) 3 }] with [NO]BF 4 .