The field of diborinane is sparsely explored area, and not many compounds are structurally characterized. The room-temperature reaction of [{Cp*RuCl­(μ-Cl)}2] (Cp* = η5-C5Me5) with Na­[BH3(SCHS)] yielded ruthenium dithioformato [{Cp*Ru­(μ,η3-SCHS)}2], 1, and 1-thioformyl-2,6-tetrahydro-1,3,5-trithia-2,6-diborinane complex, [(Cp*Ru)­{(η2-SCHS)­CH2S2(BH2)2}], 2. To investigate the reaction pathway for the formation of 2, we carried out the reaction of [(BH2)4(CH2S2)2], 3, with 1 that yielded compound 2. To the best of our knowledge, it appears that compound 2 is the first example of a ruthenium diborinane complex where the central six-membered ring [CB2S3] adopts the chair conformation. Furthermore, room temperature reaction of 1 with [BH3·thf] resulted in the isolation of agostic-bis­(σ-borate) complex, [Cp*Ru­(μ-H)2BH­(S-CHS)], 4. Thermolysis of 4 with trace amount of tellurium powder led to formation of bis­(bridging-boryl) complex, [{Cp*Ru­(μ,η2-HBS2CH2)}2], 5, via dimerization of 4 followed by dehydrogenation. Compound 5 can be considered as a bis­(bridging-boryl) species, in which the boryl units are connected to two ruthenium atoms. Theoretical studies and chemical bonding analyses demonstrate the reason for exceptional reactivity and stability of these complexes.

Thermolysis of [Cp*Ru(PPh2 (CH2 )PPh2 )BH2 (L2 )] 1 (Cp*=η(5) -C5 Me5 ; L=C7 H4 NS2 ), with terminal alkynes led to the formation of η(4) -σ,π-borataallyl complexes [Cp*Ru(μ-H)B{R-C=CH2 }(L)2 ] (2 a-c) and η(2) -vinylborane complexes [Cp*Ru(R-C=CH2 )BH(L)2 ] (3 a-c) (2 a, 3 a: R=Ph; 2 b, 3 b: R=COOCH3 ; 2 c, 3 c: R=p-CH3 -C6 H4 ; L=C7 H4 NS2 ) through hydroboration reaction. Ruthenium and the HBCC unit of the vinylborane moiety in 2 a-c are linked by a unique η(4) -interaction. Conversions of 1 into 3 a-c proceed through the formation of intermediates 2 a-c. Furthermore, in an attempt to expand the library of these novel complexes, chemistry of σ-borane complex [Cp*RuCO(μ-H)BH2 L] 4 (L=C7 H4 NS2 ) was investigated with both internal and terminal alkynes. Interestingly, under photolytic conditions, 4 reacts with methyl propiolate to generate the η(4) -σ,π-borataallyl complexes [Cp*Ru(μ-H)BH{R-C=CH2 }(L)] 5 and [Cp*Ru(μ-H)BH{HC=CH-R}(L)] 6 (R=COOCH3 ; L=C7 H4 NS2 ) by Markovnikov and anti-Markovnikov hydroboration. In an extension, photolysis of 4 in the presence of dimethyl acetylenedicarboxylate yielded η(4) -σ,π-borataallyl complex [Cp*Ru(μ-H)BH{R-C=CH-R}(L)] 7 (R=COOCH3 ; L=C7 H4 NS2 ). An agostic interaction was also found to be present in 2 a-c and 5-7, which is rare among the borataallyl complexes. All the new compounds have been characterized in solution by IR, (1) H, (11) B, (13) C NMR spectroscopy, mass spectrometry and the structural types were unequivocally established by crystallographic analysis of 2 b, 3 a-c and 5-7. DFT calculations were performed to evaluate possible bonding and electronic structures of the new compounds.

The chemistry of ruthenium-borane complex, [Cp*RuCO(µ-H)BH 2 L] (Cp* = η 5-C 5 Me 5 ; L = C 7 H 4 NS 2), 1 with various alkynes has been explored. Photolysis of 1 with alkynyl-Grignard, [HC≡CMgBr] in toluene led to the isolation of vinyl hydroborate complex [Cp*Ru(µ-H)BH{HC=CH 2 }L], 2a as a sole product. Compound 2a can be viewed as a ruthenium-borate complex with an ethylene moiety. Further, the chemistry of 1 with various internal and terminal alkynes has been performed in photolytic conditions. Photolysis of 1 with [RC≡CR] (R = CO 2 Me) yielded vinyl hydroborate complex [Cp*Ru(µ-H)BCl{RC=CR}L], 2b. Terminal alkynes [HC≡CR] (R = Ph or CO 2 Me) under the same reaction conditions led to the isolation of metal vinyl complexes [Cp*Ru(CO)(C 2 HR)(L)], 3a and 3b (3a: R = Ph; 3b: R = CO 2 Me). In addition, DFT calculations were carried out to analyze the bonding and electronic structures of these new compounds.

Building upon our earlier studies of cobaltaheteroboranes, we explore the chemistry with heavier group 9 metals. Reaction of [Cp*M(μ-Cl)Cl x ] 2 (Cp* = η 5 -C 5 Me 5 ; M = Co, x = 0; M = Rh or Ir, x = 1) with [LiBH 4 ·THF], followed by thermolysis with an excess of chalcogen powders (S or Se), affords dimetallaheteroboranes nido-[(Cp*M) 2 B 2 H 2 E 2 ], 1-4 (1: E = S; 2: E = Se, M = Co; 3 and 4: E = Se, M = Rh and Ir, respectively) in moderate-to-good yields. The solid-state structures of these compounds show open-cage triple-decker clusters. Attempts to isolate the Te analogue have failed; however, in the case of cobalt, we have isolated an 11 skeletal-electron-pair nido-[(Cp*Co) 2 B 5 H 5 Te 2 ], 5. The X-ray diffraction structure of 5 shows monocapped square antiprismatic geometry, with two Te atoms in the core. To close the central four-membered B 2 E 2 open ring [a]

In an effort to generate triple-decker complexes comprising a {PdCl 2 }moiety in the middle deck, we have explored the reactivity of [(Cp*M) 2 {μ-B 2 H 2 E 2 }], 1−4 (1: M = Co, E = S; 2: M = Co, E = Se; 3: M = Rh, E = Se; and 4: M = Ir, E = Se; Cp* = η 5 -C 5 Me 5 ), with [PdCl 2 (COD)] (COD = 1,5-cyclooctadiene). The reactions led to the formation of a series of trinuclear heterometallic triple-decker complexes, [(Cp*M) 2 {μ-B 2 H 2 E 2 Pd-(Cl) 2 }], 5−8